Diet soda can mess you up. Lemon is used in the lemonade diet and juice fasting but not in the water fast. It is better to consume foods made by nature or God instead of man-made foods that are designed to make you fat and addicted to food so you make more money for them. This site on Losing Weight tells more about the best foods to eat. It also has a page about fasting to lose weight with quotes from 18 MDs.