Fluids are good depending on what the sickness is, because usually we don't drink enough when we don't feel good. Ginger ale and Sprite are good for settling the stomach especially if you are slightly nauseous. When someone is very dehydrated, or vomiting constantly, they may not be able to keep fluids down, and that calls for an ER visit. Some people tolerate carbonation better than others, if the carbonation bothers you, just stir the soda up and drink it after that.