i usually get a soda. I don't usually tip anything on about 10 cents worth of product. more reason i favor the freestyle machines. Call it cheap or whatever you want, but they push a button for 10 seconds and hand it to me. One button one inch to the left on the soda gun the bartender uses is water, which I cant imagine anyone tipping for in a bar. Just my 2 cents.
I will say if I'm there long enough to have several beverages or switch to alcohol, i'll tip a buck every other drink