What is a stupid, easy-to-make toy involving fluids?

My friends and me have this stupid science project where we have to make a toy that involves fluids. Any ideas?|||a water gun|||Water balloons. Filled with pee.|||A water balloon. They're pretty stupid, especially on a string. Say, haing them from a board and make that silly little toy with the knocking balls all those stupid CEO's like having on their desks.|||How about a bubble blowing loop - that involves using water, detergent and glycerin in the right proportions to get good bubbles.|||Baking soda rocket. See below.