A healthy diet for a pet rabbit includes hay, fresh vegetables, and water. Just like any other animal, rabbits need a clean, fresh source of enough water to drink every day. How much water a rabbit needs can depend on a few factors, such as the size of the rabbit and whether it is pregnant or nursing. A good rule of thumb is to provide 1-2 cups of water per day for every five pounds of body weight. For example, a five-pound rabbit would need one cup of water, while a ten-pound rabbit would need two cups. It is also important to make sure that the water is clean and accessible at all times. If you are not sure how much water your rabbit needs, talk to your veterinarian for specific advice.