You can make kool-aid and baking soda fizz and bubble with out using vinegar, due to the reaction they have in water.
Spray bottle with water not vinegar
(Very inexpensive experiment and lots of fun for kids of all ages)
If you are using this as a teaching experiment for older kids here is some science info. They do not react with water, but instead they react with each other when dissolved in water. For example, acids are only really "acidic" when they are dissolved in water...acidic meaning they give off H+ ions. So, since citric acid is an acid(the kool-aid), and baking soda is a base, when the citric acid(kool-aid) and baking soda dissolve in water, they react with each other forming sodium citrate, carbon dioxide and water.
I loved it when "J" would sprinkle the kool-aid/baking soda mixture on the tray not knowing what color it was and be surprised when he sprayed it.
If your kid(s) like science like we do then you have to check out some of the other fun things we have done below.