This Witch’s Brew Dirty Soda is a sparkling purple Halloween drink made with color-changing butterfly pea tea, homemade simple syrup, lemon juice, fizzy sparkling water, and a fluffy layer of vanilla cold foam on top.
It starts deep blue, but slowly becomes a vivid violet when you add lemon juice, and turns into a creamy lavender “potion” once the vanilla cold foam swirls in. It’s spooky, refreshing, and full of halloween magic of course, but the magic is really just food chemistry!
This is a fun non-alcoholic Halloween drink for parties, movie nights, spooky snack boards, or anytime you want a festive drink that’s pretty easy to make overall.
What Is a Dirty Soda?
A dirty soda is a customized soda drink usually made with soda, flavored syrup, and cream. Some versions also include fruit, citrus, or flavored creamers.
This Witch’s Brew version puts a Halloween spin on it by using sparkling water, homemade simple syrup, butterfly pea tea concentrate, lemon juice, and vanilla cold foam.
With a sparkling water base, this version is easy to customize, and the color-changing butterfly pea tea makes it so cool.
Why You Will Love This Halloween Drink
This recipe is:
- colorful and festive
- non-alcoholic
- fun for Halloween parties
- made with a natural blue-purple color
- fizzy, creamy, and refreshing
- customizable to taste
- topped with fluffy vanilla cold foam
- fun to assemble in clear glasses
It’s especially great for Halloween because the color change is part of the experience. The drink starts blue, turns violet-purple with lemon, then becomes a cloudy lavender potion once stirred with the foam, hehe.
Butterfly pea tea naturally brews into a deep blue color. When you add something acidic, like lemon juice, the color shifts from blue to violet purple, which is awesome.
Butterfly pea tea contains naturally occurring anthocyanin pigments that respond to pH. The tea starts blue, then acidic lemon juice shifts it toward violet and eventually pink as acidity increases. SpoOoOoky…
That means this drink doesn’t need food coloring to look festive. The purple color comes from the butterfly pea flowers plus citrus.
Witch’s Brew Dirty Soda Ingredients
- Butterfly pea tea concentrate. This is the colorful base of the drink. The recipe uses hot water with dried butterfly pea flowers or enough butterfly pea tea bags to brew a double-strength tea.
- Simple syrup. Simple syrup sweetens the drink and blends in easily. We use homemade simple syrup in the soda and the vanilla cold foam.
- Fresh lemon juice. Lemon juice gives the drink brightness and triggers the blue-to-purple color change. The recipe uses 1 teaspoon per drink.
- Sparkling water or seltzer. Chilled sparkling water makes the drink fizzy and refreshing. Use very cold sparkling water and add it shortly before serving.
- Vanilla cold foam. The cold foam is made with cold heavy cream, cold 2% milk, simple syrup, and vanilla. It’s frothed until thick, fluffy, and pourable.
- Ice. Use plenty of ice. Dirty sodas traditionally use lots of ice, and pebble ice gives a fun soda-shop look, while larger clear cubes may show off the purple color better for photos.
How to Make Witch’s Brew Dirty Soda
Step 1 – Make the butterfly pea tea concentrate.
Add dried butterfly pea flowers or butterfly pea tea bags to hot water. Steep for about 5 minutes, until the tea is an intense deep blue. Strain out the flowers or remove the tea bags, then let the concentrate cool and refrigerate until completely chilled. The tea should look almost excessively dark blue before assembling the drink because ice, sparkling water, citrus, and cream will all dilute the final color.
Step 2 – Make the vanilla cold foam.
Combine cold heavy cream, cold 2% milk, simple syrup, and vanilla in a tall cup or measuring vessel. Froth with a handheld milk frother until thick, fluffy, and pourable, about 30 to 60 seconds. Get the full recipe here.
Step 3 – Build your drink
Fill a clear glass generously with ice. Add the chilled butterfly pea concentrate and simple syrup, then stir. Add sparkling water.
Step 4 – Add lemon juice and watch the color change
Add fresh lemon juice and gently stir. The blue tea should shift toward a vivid violet-purple.
Step 5 – Top with vanilla cold foam
Spoon or gently pour about ¼ cup vanilla cold foam over the top so it sits like a layer of white fog. Serve immediately. When stirred, the foam will swirl into the purple soda and turn it into an opaque lavender potion.
Tips for the Best Witch’s Brew Dirty Soda
- Use a strong butterfly pea concentrate. The concentrate should look very dark blue on its own. If the finished drink looks too pale, make the tea concentrate stronger rather than adding more flowers directly to the glass.
- Add lemon gradually. More lemon doesn’t just make the drink tarter — it also pushes the color farther toward pink. For a witchy violet drink, use the smallest amount that reliably gives you a vivid purple color.
- Keep everything cold. Cold tea, cold sparkling water, and cold foam all help the drink taste refreshing and keep the layers looking good.
- Use clear glasses. The blue-to-purple-to-lavender transformation is part of the fun, so clear glasses make a big difference.
- Froth the cold foam just enough. You want foam that sits on top, slowly sinks around the edges, and creates streaks when stirred. If it sinks immediately, froth longer. If it gets stiff like whipped cream, froth less or add another splash of milk.
Cold Foam Without a Frother
Briefly blend the cold cream, milk, syrup, and vanilla until fluffy, or shake vigorously in a sealed jar. Texture will vary by method. If your frother struggles with the full batch, froth in two smaller batches.
Make Ahead Tips
You can brew and chill the butterfly pea tea concentrate ahead of time. You can also pre-mix the cold foam ingredients and refrigerate them, but froth the foam right before serving.
For a party, I’d prep the tea concentrate and simple syrup in advance, then assemble each drink individually. The visible color shift and foam can get lost if everything sits together in a punch bowl.
Halloween Party Serving!
For a fun party moment, serve each glass blue and give guests the lemon juice separately in a tiny pitcher, dropper, or small cup. Let everyone add the lemon themselves and watch the drink turn purple before topping with vanilla cold foam!
Troubleshooting
My drink looks too pale. Make the butterfly pea tea concentrate stronger next time. The concentrate should be very dark blue before dilution.
My drink tastes watery. Add more simple syrup rather than necessarily increasing the tea. Try increasing the syrup to 2 tablespoons if the drink tastes watery.
My foam sinks right away. Froth it a little longer so it becomes thicker and fluffier.
My foam is too thick. Try again and froth it a little bit less, or even add another splash of milk.
The cream looks a little streaky. Some tiny feathery streaks can happen when cream meets acidic soda and may actually look great. What you don’t want is obvious cottage-cheese-like separation. If that happens, reduce the lemon, make sure everything is very cold, and keep the cold foam on top until serving instead of stirring it in early.
FAQ
What does Witch’s Brew Dirty Soda taste like? Think light vanilla-lemon cream soda, with the tea in the background.
Does butterfly pea tea taste strong? Not really. In this recipe, the butterfly pea tea is mainly used for color. The drink should taste more like a sweet, fizzy vanilla-lemon soda.
Can I make this ahead of time? You can make the butterfly pea tea concentrate ahead and chill it. You can also mix the cold foam ingredients ahead, but froth the foam and assemble the drinks right before serving.
Can I make this dairy free? You can try barista-style oat milk for a dairy-free cold foam, though the texture will vary. This variation may need some experimenting to get the foam texture you like.
Where do I buy butterfly pea tea? This is the kind of butterfly pea tea I used. Look for dried butterfly pea flowers or butterfly pea tea bags online. Choose a product that is explicitly food- or tea-grade.
Witch’s Brew Dirty Soda for Halloween
This Witch’s Brew Dirty Soda is a sparkling purple Halloween drink made with color-changing butterfly pea tea, lemon juice, homemade simple syrup, and vanilla cold foam.
Butterfly Pea Tea Concentrate
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Make the butterfly pea concentrate: Add butterfly pea flowers or tea bags to 2 cups hot water.
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Steep for 5 minutes, until the tea is an intense deep blue.
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Strain out the flowers or remove the tea bags. Cool, then refrigerate until completely chilled.
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Make the vanilla cold foam: Combine cold heavy cream, cold 2% milk, simple syrup, and vanilla in a tall cup or measuring vessel.
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Froth with a handheld milk frother until thick, fluffy, and pourable, about 30 to 60 seconds. Do not whip to stiff peaks.
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Assemble each drink: Fill a clear 12–16 oz glass generously with ice.
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Pour in ½ cup chilled butterfly pea concentrate and 1½ tablespoons simple syrup. Stir.
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Add ½ cup chilled sparkling water.
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Add 1 teaspoon fresh lemon juice and gently stir, watching the blue tea shift toward violet-purple.
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Spoon or gently pour about ¼ cup vanilla cold foam over the top.
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Serve immediately. Stir before drinking if desired.
Add lemon gradually. More lemon will shift the color farther toward pink.
Use very cold sparkling water and add it shortly before serving.
If the foam sinks immediately, froth longer. If it’s too stiff, froth less or add a splash of milk.
Some light streaking is normal when cream meets acidic soda. To help limit separation, keep everything cold and don’t stir the foam in too early.
For a party, make the tea concentrate ahead, but assemble each drink individually.