First did your cat get into anything that you know of?
Cats don't eat if they don't feel good (dogs will) so you must first figure out the source of the upset tummy. Has your cat been urinating? This sounds funny but if a cat can't urinate they will vomit and act lethargic (especially males). If not get your cat to the vet ASAP this is an emergency! Vomitting may subside but if your cat still doesn't eat today I would highly recommend getting him/her to the vet - there can be a number of problems that cause the vomitting. This question has lots of little twists for an answer so I guess I would call and talk to a vet technician at your vet clinic - they should be happy to help you and try to narrow down the possibilities. I hope your cat feels better!

please take the cat to the vet immediately. :)

Maybe he just needs something easy on his stomach for a little while mine went through the same thing. She ate something bad and it upset her stomach so I went to the local farming store and bought kitten formula its just like what you feed babies but its for kittens who lose their mothers. She drank i like it was going out of style and it eased her stomach. Now shes back to eating regular cat food. But I was glad I found something she could keep in her stomach while she got over whatever it was. I wouldn't have wanted her going hungry.

I was wondering if this cat was throwing up consistanly the whole night or just a few times, then won't eat or drink.
Sometimes animals get sick at their stomachs just like people. They know when to eat and drink when they don't feel well. I would watch this cat to make sure this does'nt go on for to long. The main thing is dehydration, watch for this by picking up the cats skin and seeing how long it takes to retract. If you feel this cat is dehydrating, you can get pedialite or gatorade and use a syringe to give this cat fluids. You may also try small amounts of cream or broth to see if the cat will drink. I have had alot of luck with sick animals using the flavored liquids, and canned food which contains liquid to, it will help keep them hydrated. That is the most important thing.
A rule is a sick animal will not eat or drink, but it does'nt determine how sick the animal is, so I would try an at home cure first, at least a couple days.
The cat can go without food for a while, but if you cannot get any fluids down him/her or they are not willing themselves, then get the cat to a vet.
I hope this kitty gets feeling better.

Your cat may be sick or may have parasites which can cause the vomiting. A cat that won't eat or drink can get very sick, especially after one day has passed. The cat can get dehydrated. Your cat needs to go to a veterinarian if the vomiting doesn't stop after one day. Hairballs can cause vomiting, but most cats will still have an appetite after they've vomited up the hairballs.

If your cat has a fever, or is just laying on his/her side, then a vet is needed right away. If your cat is making sounds as if in pain, then a vet is needed. The problem could be with the intestines. Watch the litter box to see if the cat is going. If not, it could be a blocked bowel problem. That condition would also need a vet.

Sometimes cats can get the flu just like a person can. The cat will have similar symptoms, such as a runny nose, cough, fever, dehydration and loss of appetite. A vet has the proper cold medicine for cats, as they can't take medicines that are meant for humans. If it's just a 24 hour virus, the cat will recover after one day without having to see the vet.

Try giving the cat a little bit of water in a spoon or eye dropper. If your cat spits out the water, try again in a half hour and then again. Also try giving your cat his/her favorite meal. There is no way to treat a really sick cat at home without a veterinarian. The cat could need medicine or an IV.