I envision a special stall - if not a designated room ( the door of which displaying a sign of a stylised man blowing chunks or woman repectively ) especially for throwing up. Essentially the facility would look somewhat like a normal toilet -flushing facility etc but more ergonomically, and functionally designed to go about the deed as unpleasantly as possible. Each side of the enlarged bowl would have handles, on the ground vinyl cushioned knee rests, and a face sized paper towel dispenser near by.

As you exit there is a mouth wash fountain and mint dispenser so as to disguise any nasty bile aftertaste. By getting the punters back to the bar looking presentable the cost of building the facility in all bars would be outweighed by their return to more drinking. It would also save cleaning up vomit from the normal toilets.

Drinking and vomiting go hand in hand (or finger in throat) - so its surprising that there is no accomodation for what happens so frequently in such places.