I think I may have found a bit of an exploit in the bar job. If you bring the patrons the wrong drink they will protest, and one of your choices is to share their drinks, which will not just make them accept it but also make them give you a fairly big tip. If you ignore what they order and bring them water instead you'll essentially assure that you get a decent tip for drinking nothing but water. I haven't actually tested it, but it seems like it would work