My brother owned a bar when I was in college, and when I was home for breaks, I'd work there. I got to be friends with the bartenders and the regulars, and people often wanted to buy me a drink. One time, I'd really had enough and didn't want another, but a friend/regular customer insisted. The bartender winked at me and poured me a club soda with lime. Looks just like a gin and tonic, so you can let someone buy you a "drink" without going overboard on alcohol.