This is the time of year when Jews around the world celebrate Yom Kippur, the Day of Atonement, with a fast (from sundown to sundown). There are always articles in the Jewish magazines on foods to break the fast, usually suggesting dairy foods. I think they suggest dairy foods for a couple of reasons. First, they are supposed to be easier to digest. Then, dairy foods have a history in Jewish tradition of being foods of mourning, which atonement involves.
One thing I know: when I break my fast, it'll be important to drink lots of fluids -- fluids are more critical than food. Also, I once had surgery and the doctor said that simple, starchy foods -- such as mashed potatoes -- are the easiest to digest.