I understand that it's basically hunch punch, with the occasional disgusting addition (chocolate syrup, orange juice, milk; depends on the sadism level of thems in charge). In a (clean) toilet bowl.
I'm told that there will be nonalcoholic grog for teetotalers - in a potty chair.
And you drink if the President of the Mess tells you to drink, f'rinstance if you violate any of the rules. Although if your guy is really responsible for your every move, maybe he should drink the grog if you break the rules.