I have a confession to make. I drink a lot of Diet Shasta, frequently guzzling straight out of the 3 liter bottle. Now, you can almost see one kinda explode:

I've used the bottles for various purposes, such as carrying drinking water when hiking and backpacking, and also carrying several of them filled with non-potable water on training hikes; when I get to the top of something I empty out the water. I've dropped them on rocks and such, and I've only had one of them create a spill. That was in a 99 Cents Store parking lot, and, while I didn't write anything down, I seem to recall that that was a cap-related issue.

I think it would be possible to fashion a fairly cheap way to do this that would create a very large explosion; perhaps with a time-release setup of some kind (candy coated with something else) or something that would automatically release a large number of candies all at once in the bottom of the bottle rather than simply putting them in the top by hand.