I have a pet hamster and I do keep hoppers overnight. I have the "gut load" mentally like I do with insects, even if it does nothing for mice lol, and I feel better knowing it has a good meal before becoming dinner. I feed it what I feed my hamster, but much less in quantity because it is so young.

I give it 2 cheerios, small piece of green veggie and a dog kibble. The hopper usually can eat all of it overnight or hide the extra somewhere. Water is in a small reptile dish that I could not use for my lizard. I don't use water bottles for my hamster or bunny. They never drink enough and it seems like it is such a struggle trying to get enough water. Every hopper I bring home would drink from the bowl. I use a small plastic lid as a food bowl. I keep them in a 6 qt tub that I bought extra and use papertowels as substrate. They poop a lot and likes to hide inside the papertowels.

I don't know about you but just by keeping a live hopper overnight makes me feel guilty every time I feed him to my bp. I know it must be done, but it bothers me after the deed is done and I have to clean an empty tub and find traces of it living there, ie hidden stash of food. It would be extra hard for me to keep it longer than that.