My ideal movie, and a scenario I don't see all that often in porn, is someone being so desperate to pee in a semipublic place, but unable to just piss on the floor or wet themselves, so they get another person to drink their urine.
At least two people are stuck someplace like an elevator, office, or car, and can't leave for whatever reason. Person A really has to piss, like on the verge of an accident.
But due to social pressure, they can't let it be known that they peed. No one is around right now, but people will be around soon. They can't wet themselves because people would see th