You can soak his normal pellets in water and make a slurry that you feed by syringe. If he’s willing to eat fruit, he’d get sugar from that. Or else you can add some baby fruit puree to his pellet mush. Pear is often a favorite taste. Fruit has glucose that acts quickly. I suppose honey would do the trick too (but i haven’t tried honey myself with my buns), but don’t give too much or his tummy might get upset.

There are critical care products for rabbits, the most well-known one is Oxbow’s. Not all pet stores sell it though, so you might have to order it online. Meanwhile, pellets with water is good. You can add plain canned pumpkin mash (not pie filling) to the pellet mush for extra fiber. That taste is also often appreciated by a bun.

He should move around a little to help his gut get going, and hydration is very important.

ETA: Kuro syrup seems to be made from very dark, unrefined Japanese sugar. You could use some other form of unrefined sugar like muscovado and add water. Here’s a recipe. https://www.delectablehodgepodge.com/recipes/kuromitsu.html

But if you have honey, I’d use honey and water. 

Hi. How frustrating, annoying and enraging
You won’t be leaving him with the same ‘friend’ again huh!
Follow all of bam’s advice – there’s nothing more to add…
((( get better bunny )))

Yes please syringe feed as soon as you can as they said. Is this vet rabbit savvy?? Please call around to every pet shop ask for oxbow critical care! Praying for your little love.

I know the syringe feeding may seem like it isn’t working but you have to go slow and get it on the side of his mouth so he can’t spit it out. You have to do this as often as needed. It’s the only way he I’ll avoid stasis.

Does this vet not have critical care? I buy it from Amazon.

((((((VIBES)))))

Is there any chance they will allow you to come and visit?

I don’t like the sound of their absent optimism…. i always think that negative vibes or less effort to treat doesn’t give an animal (or human) the best chance…
Syringing is the only way to get food in him, and him resisting is in a way a sign that he has strength left.
You must always be careful to make sure he swallows each mouthful rather than force feeding him too fast.

Anyhoo, his immediate fate remains in the hands of the vets now… (((( get well bunny ))))

I’m sorry the vets aren’t optimistic. I agree with Vienna, that he fought being syringe-fed was a good sign – a rabbit only does that if it has fighting spirit left in him. Warming up, IV fluids and oxygen are excellent supportive care measures.

Please recover (((((Luca)))))

Warming up, IV fluids and oxygen are excellent supportive care measures.

I agree. 

Sending {{{vibes}}} for (((Luca))). I hope they are able to get him stable and some food into him after.

Improvement is still improvement. Glad he is hanging on (((((VIBES)))))

Go Luca GO !!!!!!!! ((((( come on little guy )))))

((((((Healing Vibes for Luca))))))))

More healing vibes for (((((Luca)))))

Come on Luca, you can do it!!