-take milk, to make you sober pretty fast
-take applesauce (how do you call it, for you dutchies Appelmoes, in brasil they say compote del masa (or something:P) --> applesauce takes away strong smells, like garlic and alcohol
eat a lot before drinking, that way you can drink more (and If you do get drunk, you will digest it faster, you do get a beerbelly though :P)
good luck
on a side note...I managed to do it a couple of times, I thought they hadn't noticed, but at one of the final lessons one of the teachers said (when I came in class too late):"have you been drinking again" :P And I knew what he meant, wasn't angry about it though ^^