I understand your diffuculty.... fellow bartender here at 3 months without a drink. It does present its own set of challenges. I am lucky that my current establishment doesnt encourage drinking behind the bar... but I have worked at spots that do...so I understand. a few ideas that come to mind is say you are on antibiotics or trying a new health kick... like a sugar detox or cleanse of some sort... I used that for the first month when people would ask if I wanted to meet up for a drink. Or just say you are taking a break... giving thev liver a rest or something... come up with a good self deprecating joke. Its hard because you dont want to make your customers uncomfortable drinking, but they might be used to drinking with you. I used to know a bartender too who kept iced tea in a jameson bottle and would pour herself a shot of iced tea from the bottle when customers wanted to do a shot... looked like jameson to them and nobody ever was the wiser.