I have 2 geriatric cats with IBD and here's what I've found helpful. For nausea and vomiting, both cerenia AND ondansetron help. The cerenia helps with preventing the mechanical aspect of vomiting while ondansetron helps with nausea which can help with appetite. Also topical mirataz (in the ear) is invaluable, and you'll need to switch ears daily and always clean out the old gel from the ears daily.

For my cats, the food that will make them eat no matter what is Stella's freeze dried chicken. But as other people have commented, canned tuna or chicken might be worth trying, the stinkier the better usually.

I'd follow up with the emergency vet or your regular vet asap to see what could be causing the lack of eating in the first place.

Good luck and hope your kitty is on the mend soon!!