It's the same rule for people who attend to football (or soocer for our US friends) matchs...
... in the case of football matches, they control every people at the entrance.
But in the LM case, it's simply impossible to do, or the officials will face to a new waterloo. And do you imagine the champoo bar with plastic bottles?
??
Just open your bar in front of the geenarle ntarnce, you juss pass the getaway every time you wanna drink...
... or you just drink can.
And hide your bottles in your pants!
Gilles