Well having a good flow of hydration (drinking water - not too much though, that is also seriously dangerous, if you drink too much liquids without excreting them cells in your body can burst) and peeing is always healthy and not great on the kidney-bladder system if it stops especially if you keep drinking water or beer.
Beer (the alcohol in it) is a diuretic, it messes with hormones making you pee a lot more - as most of us know.
So not a handy combo here..
The not being able to pee is much more typical for uppers (stims) than for psychedelics - though some psychedelics do activate the nervous system and muscles in a way. The reason here is that if muscles tighten up, you are decreasingly able to relax particular muscles you need to pee. Those muscles are not as easily controlled accurately as your normal limb / skeletal muscles. That's why the best strategy is to try and relax every muscle in your body without falling down of course. Then along with the rest, the peeing muscles should relax making it possible. But if you take too many stims this too will get very difficult.