Years ago I was in a place, 'Milk' or something stupid it was at the time, and (early on - our first order) I ask for vodka+coke. Barguy says it's only 20p to make it a double; so I say ok.
Next time I go to bar he say's 'No, You've had too much mate.' One of those things that inexplicably makes you angry many years after the fact.