Would it depend on how much you've got on the table or do most people tips more or less the same. I mean, if you've got a pile of blacks on the table and you give the waitress a red or a couple of silver, she's gonna think you're a cheapskate. But would she really deserve $25 just because you have lots money? If you are only betting silver and red and then you tip a red, your could be giving up your profit for the hour. So how much should you tip for drinks without giving up too much money or making the waitress think you are stingy??
Of course when you are playing bj you do not want to drink so I guess nobody really has this problem, but just in case...