So i tried the whole Mentos and Diet Coke phenomenon
 

Let me say i was fairly impressed. We made a paper funnell, took about a pack and half of mint mentos (it has to be mint for some reason) put the funnel in the bottle of Diet Coke and shoved as many in as we could, immediately it shot about 20 feet in the air.

Mike, this is something fun to try with your scouts.