I'm crossing my fingers here, but I've had very little trouble with passengers who are the worse for wear due to drugs and alcohol. Maybe half a dozen in 20 years? But the profile of our passengers is radically different to your average bucket-and-spade punter. We also rarely fly stag and hen parties. However, as a company we have had some dreadful incidents but I'm afraid most of these were own goals - the crews saw the warning signs and still let those they were concerned about on.
Charging for drinks is also not one of the problems we face. They are included in the ticket price, so there is no need to pre-load.
But the best way you avoid the lager louts is to have high quality gate staff who will off-load the roudies before they even get on.
PM