When we first caught our two rescue girls, neither knew how to drink from a bottle, and I used a bowl. Gina soon switched to the bottle after watching our boy buns, but Jenny stuck exclusively to the bowl. We got her one of the metal ones that attach to the side of the cage, and she seemed happy with that.
Post spay, Jenny’s water consumption dropped to a worrying low amount, and I used the wet greens approach to getting water into her, and also syringed some. I used puppy training pads across the whole base of both girls’ cages, so I could see just how much they did pee, and I’m glad I did, as I could see straight away when they did go.
A few days ago, Jenny mastered the knack of the water bottle, and was like a child with a new toy, as in she just stood by it and drank and drank and drank. So I went from worrying she wasn’t drinking enough, to worrying she was drinking too much.
So, I would say, if you can, leave the bottle, and the bowl, and if you can see he is peeing in the litter tray, then he is getting enough. Lots of leafy greens will give water, and I also used a few slices of cucumber when Jenny wasn’t drinking. Melon is also good for getting fluid through, though maybe a bit high in sugar for too often?