Supplementary water is generally not needed since there is sufficient water in both breast milk and modern infant formulas. For the infant who is gaining weight well, supplementary bottles of water may be given as desired. They should not be sweetened with sugar or any other sweetener. If you offer plain water and it is refused, he/she is not thirsty. If he/she is thirsty, the water will be taken quite well. If he/she consistently refuses water, then it is not necessary to offer it at all.