Welcome to Pet Talk. I'm so sorry to hear about your kitty. What kind of food are you feeding him? If he's only eating dry food then I'd try mixing in some wet food because this will add more moisture and will rehydrate him. You can also add some chicken broth or more water to his food to increase his water intake. Sometimes my boys eat so fast that they throw up too. Now I feed them 3 smaller meals about 30-45 minutes apart and this seems to be working. I do this 2 times a day and they eat dry and wet food mixed together. I hope he feels better soon. Good luck and please keep us updated when you can.