Water is a reptile's most important nutrient. Nothing is more important in keeping a reptile healthy than providing an easily accessible, clean water source. It is best to provide water in a large shallow dish. Change the water at least every 24 hours. Some lizards - chameleons and anoles, for example - will not drink from bowls. Give them water by spraying a mist on plants or the sides of their cage.
For more information, please read the story Reptiles Need Water, Water, Water.