You can try flavored water
found this on "life.familyeducation.com":
In a survey designed to measure the amount of phosphoric acid in twenty different soft drinks, the following were found to contain the highest amounts: Tab, Coke, Diet Coke, caffeine-free Coke, and Mr. Pibb. The formulas may have been changed for the better since this survey was conducted. Read labels. By the way, Pepsi Free, Diet Pepsi Free, Like Cola, 7-Up, and Mountain Dew had no phosphoric acid in them. This, however, does not mean that these products are free from the other problems true of soft drinks.
Phosphoric acid is mainly what causes yellow teeth.