OK I think pretty much everyone knew about this except for me but I want to share with you just in case there's some other poor soul out there who is just as unaware as me. Apparently if you mix Mentos candy and any kind of soda you get a soda geyser of sorts. Many poor fools have taken it upon themselves to a) try the experiment b) record the entire thing and c) post it on YouTube for the collective benefit of the citizens of the internet. There are quite a few of these videos out there . A YouTube search for coke + mentos or pepsi + mentos should pull up most of them. As for what causes the reaction, you can find a pretty decent explanation on Steve Spangler Science. And in case you're too lazy to read the whole thing, here's the gist of it:
As soon as the Mentos hit the soda, bubbles form all over the surface of the candy...When all this gas is released, it literally pushes all of the liquid up and out of the bottle in an incredible soda blast.See, I do all the work for you.