Eating and drinking but throws it back up

Sounds like a vet visit is in order.

What eats and drinks and throws it back up? Are we asking about a child or an animal ? What kind of animal, dog, cat, rabbit, bird ?

I know you have it posted in the animal forum but sometimes people make mistakes in where they post.

How old is the dog? Is he drinking none stop, and then throwing it up? You said he's eating, is his appetite normal, or waning? Also, how is is output (poop and pee)? How long has this been going on for? Has there been a change in food, medication, anything?

Need a few questions answered before we can offer a guess, but I have to say, even if you come back and answer, we can really only guess. The best thing to do, if you're concerned which you obviously are since you posted about it, is to go to the vet.

Good luck.