Just carry a glass of wine around. Sounds weird, but when you go to the bathroom, pour some down the sink, without anyone noticing of course.
If it's busy enough, leave your glass somewhere and go get another of a different kind. Yes, this is wasteful, but if you're really worried about getting noticed, it's good cover. And really, how much are they expecting you to drink? Also, you can sip without really taking in anything. Again, sneaky but it works!