What is an acid anhydride that makes a refreshing drink?

Question

This is for a chemistry scavenger hunt. Everything has to be found in the house or be a household product. I know what an acid anhydride is, but I don't know any drinks that contain acid anhydrides.
I was thinking it could be any of those powder drinks. Such as Koolaid or powdered lemonade. Where you have bags of powerder, and when you add them to water, it makes a drink.
I'd appreciate any help I can get. Thanks.

Answer 1

You're right about lemonade. Anhydrous citric acid is found in lots of drink mixes. Anhydrous just means "without water"