Been admitted both voluntarily and involuntarily multiple times, in multiple hospitals. The experience varied a LOT from one hospital to the next. Some were godawful and I got out asap, others were really helpful environments, some were in between.
The variation on what I couldn't take in depended on both the individual hospital's policy. Some places I wasn't even allowed deodorant (even voluntary, because of the potential access from higher risk patients). Other places, they just asked me not to bring any drugs or alcohol (but they also booted you out quick smart if you crossed the line).
Involuntary admissions have been pretty shitty experiences for me every time. And yeah, sometimes the hospital itself made it hell. But I needed to be there. It kept me alive. Mostly though, it was gonna be a pretty shitty experience regardless because I was in a pretty shitty headspace, and at least they kept me safe.
Bring in hospital has never been a thing I've enjoyed - I know that for sure. But sometimes it's necessary. And if it's necessary, most hospitals, as shitty as they are, are better than the alternative in the long run if you need to be there.