The answer to this question is a nice, clear, simple, “It depends.”
First, if you avoid alcohol for religious or health reasons, or you just don’t like the taste, then you must already know how to decline an invitation to imbibe. (If not, now is the time to work out a brief, polite, low-key, non-sanctimonious and good-natured refusal.)
Second, if you’re going to be driving later, then it’s also a no-brainer to say, “Thanks, but I have a long drive ahead of me.”
Which brings us to the big question: Is there ever a time when it’s OK to accept a drink at a job interview? Here’s where the “it depends” comes in. If your meeting is taking place at a dinner (or happy hour) where everyone else present is drinking, and if you’d normally enjoy a drink under these circumstances, and if you are capable of ingesting a bit of alcohol without it affecting your performance, then you might say yes. After all, it’s important to be yourself at an interview.
However, you will still need to meet all of the following criteria:
Have one drink only. Take your time with it. In fact, feel free to not finish.
Act casual. Take an occasional small swallow and otherwise ignore the drink’s presence. Please don’t sit there clutching a glass (or, worse, bottle) in your hands — this is not the mental image of you that you want a future boss to have.
For every sip of alcohol you take, have two or three sips of water. This is especially important if you’re thirsty and might be tempted to down that beer purely for the hydration.
Important: Remain aware that just because you’re sitting in a cozy restaurant sipping a nice glass of wine it does not mean that your interviewer has stopped interviewing you. You are still being evaluated. Comport yourself accordingly.
Finally, always remember that you can never go wrong ordering sparkling water or soda if that’s what you feel like having. You don’t even need to explain why. Just say, “Thanks but not tonight,” smile and change the subject. If they push you to drink — well, you might want to ask yourself if these are the kind of people you want to work with.