Why does my cat throw up right after drinking water?

Usually it’s the speed, not the water. A cat who gulps a large amount quickly, often after exercise or a long stretch without drinking, can bring it straight back up. The same thing happens with food. Try offering smaller amounts more often and a wide shallow bowl that slows the gulping. If the vomiting is frequent, the water comes back up every time or she seems to want to drink a lot more than usual, that points to something medical rather than simple speed.

When to call a vet: Repeated vomiting after drinking, or a sudden jump in thirst, should be checked by a vet for kidney or other issues.