Welcome to SR dentist.
This is a tough situation to be put in so early in your sobriety. I would suggest a little white lie may help you get through without lookimg unsociable.
I would say that I was on antibiotics and the doctor said no drinks and you take your health seriously. It is flu/cold season so a throat infection is quite believeable.
I used this several times when I was an on the road salesman when i had to drive customers and entertain them.
Another thing I did was arrange in advance with the waiter to bring me coke only when I ordered rum and coke so the customer would think I was drinking with him. That one always worked but doesn't sound like an option in your case.
Good luck.