What's the least expensive item I can order at a bar, not seem suspicious, but also meet the guidelines?
I feel that soda wouldn't pass... nobody sits at a bar drinking NON-Alcoholic drinks, as you say.
At the airport bar shops you are not allowed to order alcohol. I order a soda water with lemon and a soup or chowder. I know this is somewhat different than a dinner shop, but I don't feel funny about it.