I saw a girl get out her 12oz tube of sunscreen and take a shot from it. Those tubes don't unscrew, so it must have been tricky getting the leftover sunscreen out before putting the alcohol in. On the other hand, if you filled it with Malibu, would you be able to tell? Hey, maybe the recipe for Malibu is vodka "cask aged" in sunscreen bottles.
Nothing will beat the time a couple years ago, though, when these guys were passing around several boxed-wine bags - the big 2L or 3L ones. I asked them how they managed to smuggle those in and they said, easy: we just came to the park a couple days before they put up the fences, and buried them in the woods!
Drunkenness favors the prepared.