Ok that is just one of the best pranks I've seen in a long time. I gotta find someone to play it on. Unfortunately I'm the Coke addict among my friends, in fact if any of them see this I'll be the guaranteed target
By the way I've heard it works with any carbonated drink and that diet coke is preferred over regular mainly only because without the high sugar content it's much
easier to clean up afterwards. There are supposedly videos on youtube of people trying to repeat the effect internally but none seem to have the common sense to actually attempt it in a way which might have worked.