[thematt]

I would be honest with them but if you're that concerned about "fitting in"...just order a soda. If somebody asks, tell them you prefer mixed drinks and that it's a rum and coke. Nobody will know the difference.

[rubergly]

An environment which requires constantly lying to fit in dosen't sound like one anyone should want to be a part of.

[gaius]

Or that you're driving/riding, or that you're in training for a Marathon... There are loads of socially acceptable answers if you don't feel comfortable saying "I don't drink" (not that there's anything wrong with that).