Few questions:

1) Were you given pain medication to take home?
2) Is Bunny jumping and climbing? Following a neuter, his area and movement should be restricted so he does not irritate the sutures. Even if he feels okay to jump, he doesn’t understand the ramifications that movement has on his recovery.
3) Is he grinding his teeth at all? This is a sign of pain, so if it occurs, he needs pain medication.
4) Are you checking his surgery site at least once per day? You’ll want to do this to ensure it’s not getting infected, irritated, and or swollen.

Not drinking after a neuter is common. Give him water by extra wetting his veggies and syringe feed water if necessary if you see he isn’t peeing as normal.

Not eating is difficult as generally he may feel groggy and bad after a neuter, but eating is important. If it’s a general cold shoulder to hay, pellets, and veggies, call your vet and let them know. If it’s just a cold shoulder to hay, give him a bit more time to settle in. Continue feeding everything as usual, but also do your best to make the hay as appealing as possible. If it means replacing untouched hay with even fresher hay twice a day, do that. If it means giving him a favorite kind, like orchard over Timothy, do that.

If he’s pooping and peeing, and his under-area looks healthy, he’s recovering as usual.

Keep us updated and let me know about my questions.