My first question would be if your cat vomits watery fluid shortly after she drinks water? If that is the case then she is drinking too fast and the water is not even going into her stomach before she regurgitates it back up. Sometimes this happens because the water is too cold, sometimes this happens because of a weakness in the diaphragm in the stomach is not 100% below the diaphragm. This syndrome is calledhiatal hernia – it is a functional problem similar to gastroesophageal reflux disease in humans who are told to take antacid and sleep sitting up.
A veterinary chiropractor can fix this situation quite easily in many cases. If your cat is vomiting water other times then there maybe something else, more serious going on. It’s possible your cat has heart disease and is coughing and gagging, it’s possible your cat has a fungal infection.
Either these conditions requires veterinary examination and usually a chest x-ray. So if your cat is doing this than really pay attention to what comes before to help in the diagnosis so your cat gets the proper care she needs.