It's quite clever what they did for that whole scene. Because I've done this before, and it really isn't very easy to be as controlled as they were.
They were obviously very well prepared, because it seemed they drilled holes in the plastic caps, and did some kind of pulling mechanism with strings to drop the mentos in. And it cannot be just one Mento, it has to be TONS to get that kind of huge pressure and strong reaction.
Just one Mento is pretty crazy, but a whole bunch is even better
. The thing is, if you try and drop in a 'stack' of them all at once, chances are, only a few will get in. Because once you drop in the first one, the reaction is super-fast and it just blows out the top and all your Mentos won't make it in
. So they did a good job to get the most power out of the soda. Spent a lot of money and time on it too I'll bet :o