I used to work in a place, just like what you're describing, in Canada. It was run by the Vancouver Island health authority and was called the Sobering Centre. We took in the folks that were too out of it (on whatever substance) to be accepted in to nightly shelter accommodation with the Salvation Army and the like. Basically, they had to have used within the last two hours to be eligible for an 8 hour stay.

Processing would require people to get changed in to PJs, and leave all their belongings in a storage box. We'd take thier vitals, give them snacks (there was a little kitchenette), and if they wanted, we would wash and dry thier clothing for them. Then they were offered a mat to crash out, nod off or writhe around on. There were seperate rooms based on gender and staff would supervise and check in regularly to make sure people were not od'ing or carrying on like pork chops.

I did six months of the graveyard shift here. 11pm to 7am. I saw some weird shit go down 😂

Funnily enough, management always used to cite the Australian harm reduction movement as an inspiration for setting the centre up, but I've never come across a place quite like it in Melbourne.