Something I did once was to approach the bar person straight away and explain the situation to them. I said that if anyone tries to buy me a drink they'll order a vodka, lime and soda or a gin and tonic, and could the bar person please exclude the alcohol? Bear in mind this was a session which started at 2pm, so it was pretty quiet at the time. This trick would fail of course if there was anyone else in the round who wanted the same drink as you. I tried to stay out of rounds and just got DH to buy our drinks, so I would clearly ask him to get me a G&T, and he would just get the T.

Most of the time I say I'm driving.

I've got a friend who knows I've been TTC, but doesn't know I'm pregnant. She's also TTC so abstains herself in the TWW. If she notices I've been 'driving' a lot I'll just say I'm in the TWW.