While being penetrated

...only while being penetrated. In this reality, after people turn 18 they suddenly develop a psychological quirk that completely prevents them from relaxing their bladder unless something is inside one of their holes. Upon waking up in this universe you will find this applies to you as well. For a man to pee he must be penetrated anally, and for a woman to pee she must be penetrated either vaginally or anally (though vaginal penetration is much more effective at helping her bladder relax). Keep in mind this is purely psychological; if your bladder fills up enough you will eventually pee even if you aren't being penetrated, but the experience would be incredibly unpleasant.

Pretty much anything can used to penetrate a person to help them pee, whether it's a couple fingers, a hairbrush handle, a man's penis, a dildo, etc. However, the bigger the object is the easier it is for the person's bladder to relax, so it's common for someone to ask the nearest man to penetrate them with his penis, or to carry a dildo with which to help themselves. Obviously, this reality has a casual attitude towards sexual penetration, so being bottomless in public is a-okay, though full nudity and other sex acts may be frowned upon. If a man accidentally ejaculates inside a person while helping them pee, it's treated like an extremely embarrassing but ultimately harmless mistake.

But after being penetrated, where do you actually pee? The answer is pretty much anywhere, as long as it doesn't make too much of a mess. You can use a toilet, sink, or bathtub, or a portable receptacle such as a cup or bucket, or just go on the ground outside. Some people may allow you to pee on their floors too. If a person is helping by penetrating you, you're expected to find a place to pee nearby rather than make them go with you to look for one.