...and it's all analog!
I've mentioned this before but I'm not anyone has actually tried it, so...
1. Remove anything soft from the bathroom - towels, shower curtain, etc. Preferably, there will be lots of hard surfaces, like mirrors and tiles.
2. Insert a small powered monitor in there. I prefer a 4" speaker with the lows rolled off.
3. Send your reverb bus to a spare audio interface output, and run that to the speaker.
4. Put a mic in the bathroom, behind the speaker, and run a cable from it to a mic input in your audio interface.
5. Close the bathroom door.
I record the reverb sound into a track so I don't have to leave the speaker and mic set up
But wait! There's more!!
Changing the mic position even a little bit gives a slightly different sound, sometimes changing the phase makes a difference as well. The main "rule" is I try to keep the mic behind the speaker, so it picks up as little of the direct sound as possible.
Some EQ on the reverb really helps, I tend to roll off the lows and lower mids, and maybe boost the highs a bit.
This really does work!