I always keep a few in my wallet. I've given them to various people - the grandmother in line who was lamenting that she was going to have to pay for drinks on her flight to Europe, people who missed a flight or had theirs canceled, a nice seatmate - whoever looks like they could need a drink. I never realized that FAs might have to pay for drinks - I'll be sure to send some their way.

Even though they don't have expiration dates, I've always been a little hesitant to give out my old ones - has anyone had an old drink coupon rejected?