Picture of The Color-Changing Sports Drink
This blue drink turns purple then red/pink upon addition of a citric acid-boosted can of Sprite. It tastes good and has a similar chemical profile to a hypotonic sports drink (also see this homemade sports drink recipe). It's the kid-friendly version of the Color-Changing Martini - and it's much cheaper and more convenient than buying martini ingredients and dry ice. It's basically a classic chemistry demonstration you can drink.

Note: I published this instructable in 2010, but unpublished it while I developed it further as a submission to the American Chemical Society's  Journal of Chemical Education. The article has now appeared, so for those of you who happen to have electronic access to this journal (probably because you are connected through a university network), you can find the manuscript online here.

Step 1: Ingredients

Picture of Ingredients
You'll need: 

Sprite (or other clear carbonated beverage) ~ baking soda ~ red cabbage ~ citric acid ~ tap water
klixtopher6 months ago

Thanks for this. Did it as a science lesson with my kids. Trying it with calcium bicarbonate (Tums). The color change works well, but it does leave the liquid a bit cloudy/milky, trying to let the particulates settle a bit in the hopes I can pour off a nice blue liquid. The goal is to avoid that sodium flavor. Thanks again.

makendo (author)  klixtopher6 months ago

Great! You need only a tiny bit of sodium carbonate to make it go blue - it's pretty hard to taste once you have the cabbage/sprite in there.

I used the citric acid idk why it's kind of purple, might be the lighting?
Worked so good!! Freaked my younger siblings out
2014, 2:14 PM.jpg2014, 2:14 PM.jpg
makendo (author)  Indestructibility Man1 year ago

Cool, glad it worked. Still looks pretty purple tho - did you just use Sprite without the citric acid?

gluvit1 year ago
Trying this
hotfarts1 year ago
Great stuff. I'm a chemist, and can mess with my non scientist family members with something they can see and taste, then hopefully understand. :-) Thank you!
makendo (author)  hotfarts1 year ago
Cheers, you're welcome. Have fun!
Jane Oreo1 year ago
oh. Color is very good-looking.
Ohnanka1 year ago
Will it still work if I add gin to it first? ;)
makendo (author)  Ohnanka1 year ago
Oh yes
cmanuel14 years ago
Well as jaegerschlager said in the comments of The Morphing Martini (http://www.instructables.com/id/The-Morphing-Martini/step4/Present/), you can also use blueberry.

But will the colour-change be as fast?
makendo (author)  cmanuel14 years ago
Yes, the colour change will be as fast, because the reaction is very rapid. However, exactly what the colour change is will be dependent on the exact identity of the anthocyanins, so it may be less dramatic. However, I just don't know - I may try it next time I have both dry ice and blueberries in the house...
aidylgs4 years ago
Anyone tried dryice instead of vitamin C for the color change or is it a bad idea?
makendo (author)  aidylgs4 years ago
Dry ice works well, see http://www.instructables.com/id/The-Morphing-Martini/
but the color change is less dramatic (carbonic acid is pretty weak).
aidyl makendo4 years ago
Thanks for your reply. My students enjoyed it but you are correct about a VERY SLOW color change.
makendo (author)  aidyl4 years ago
The speed of the color change will likely depend on how much baking soda you add at the start, because you need to neutralize all of it. In the video I posted for the martini, the color-change is essentially complete in about 15 seconds, but I just used a small pinch of baking soda. I'm interested to hear what was "very slow" for you (several minutes?). I agree that the change does need to be reasonably quick for best effect.
aidyl makendo4 years ago
The color change time was a little over a minute. I did use about a tsp of baking soda.
Rocky1227975 years ago
i tryed it
makendo (author)  Rocky1227975 years ago
Good stuff. Did it go red, pink or purple?
Kind of purple-pink
makendo (author)  Rocky1227975 years ago
OK, that makes sense - it's a weaker acid than citric. Hope it was drinkable as well as healthy!
Your son takes it over the top!  SOOO CUTE!

If you didn't have citric acid, could you use a crushed up Vitamin C tablet (the chewable kind)?
makendo (author)  AngryRedhead5 years ago
He's a character, all right.
A vitamin C tablet is a really good idea, even though ascorbic acid is weaker than citric - I think an effervescent vitamin C tablet would be neat (provided it was one of the crystal clear types, and didn't have any coloring), because you could drop it in the blue solution and it would bubble and change color slowly (which is always neater somehow than the rapid changes). Whether it would go pink or only purple, I don't know - I hope someone tries it. 
i did
winterfresh5 years ago
Eye-candy + tongue candy = really sweet instructable!

Really sweet instructable = I click Favorite.
makendo (author)  winterfresh5 years ago
Thanks - glad you enjoyed it.