When it comes to nosy nellies inquiring about not drinking, I'm a big fan of the broken record technique, repeat as needed:
"You aren't drinking?" "No thanks I'm not drinking." "Why aren't you drinking?" "No thanks, I'm not drinking." "Really? Can't you have just one?" "No thanks, I'm not drinking."
A few cycles and most will move on, and you have not revealed anything you didn't want to....yeah!