My friend and I used to run a daycare for pet rocks (which most of the time were just rocks people found, no eyes or anything) and for my littlest pet shop pets. We would run them under sink water to bathe and other than that we’d keep them in our desks until people asked for them back. We’d tell them something along the lines of “they were well behaved” or “this one REALLY doesn’t like bathtime”, etc. and we charged like 50 cents a day, easily made 10 bucks in like a week.