I've been using them for years for hatchlings. I love them. Not good for older/bigger snakes since everything tries to crawl in and coil up. But for hatchling balls and smaller colubrids they're great.
i use a small sized deli cup held by a pvc coupler for younger snakes and a bigger sized cup for older snakes. i don't use a lid on any of them--i've heard that hatchlings can drown if you use any sort of lid.
i've heard that hatchlings can drown if you use any sort of lid.
I've raised literally thousands of hatchlings using these cups as water holders and I've only had two of them drown. The odd thing is that BOTH of them were prarie kingsnakes and they were the only two prarie kings I've ever had.