protein water (kellogs20, designer whey protein2 go powder mixed with water, gatorade, vitamin water etc.) first two can be found in Giant food stores in the health food sections don't know about other groccery stores but expect it would be in the same place.
Another good one is miso soup or clear sushi-style broth. both really good if u need flavor.
I had my surgery a week ago today and those things got me through. Good luck, it's not so bad, you can do it!