>>42455691
Rainbow sweats a lot when she sleeps and the clouds soak it up, she doesn't have to leave to go piss either, it's very convenient, she can wake up and start her daily stress relief with it too.
Her morning clouds are disgusting, it's kind of gross she just grabbed her morning cloud and brought it over to clean Twilight with, no doubt she finds the idea hilarious. Or maybe this is something she does to ponies new to ponyville crashes them in mud and showers them in her filth.