MrsKitty, I would be the worst person to give advice on excuses why you're not drinking because I fail (and did fail) miserably. Not saying I'm alcohol dependant but all my friends thought it was extremely unusual I wasn't drinking and a couple guessed.
My feeble tactics were: Water in an empty beer bottle, just tonic with a wedge of lime so it looked like gin, I'm driving, I'm still hungover from the night before.
Funnily enough, I just popped on here to let you all know how happy I am because I've just discovered Becks Blue beer actually tastes like beer, unlike every other alcohol free beer I've ever tried that actually tastes like soggy cornflakes. It was like winning the lottery when I found out because I love a beer and especially in the summer. Sooooo, could you get yourself some of those and hide them, then pour into a glass and drink that?