"Compare Sports Drinks with the Electrolyte Challenge": in this chemistry project, students use a simple circuit and a homemade sensor to investigate the electrolytes in various sports drinks and juices.
Can a Mentos and Diet Soda Chemical Volcano Erupt?: This is an easy project. You'll get all wet, but as long as you use diet cola you won't get sticky. Just drop a roll of mentos all at once into a bottle of diet cola.