Fill a few cups with baking soda, mixed with a little bit of neon paint.
Put vinegar in a pitcher or measuring cup with spout.
(*Be sure to do this inside of a small bin to catch the overflow.*)
Go into a dark room, turn on a black light and let the fun begin!
(*A black light is necessary for this to glow.*)
She really enjoyed this, and kept pouring vinegar in the cups until it was gone! :)