Q&A: Keeping Baby Hydrated?
According to the American Academy of Pediatrics (AAP), it's best to not give your baby anything other than your breast milk for the first six months of life. Not only is it unnecessary to offer extra fluids to your breastfed baby, those added ounces of water or juice could lessen baby's desire to nurse as frequently and hurt his body's ability to absorb all of the goodies (aka nutrients) in your milk. Plus, juice adds unnecessary sugar to baby's diet. Rest assured that breast milk contains all the liquid baby needs — even if you live in a hot or dry climate. (Some experts do suggest that formula-fed babies sometimes need to be supplemented with water to help baby's kidneys get rid of the extra salt found in formula.)
Once your baby is six months old and starting solids, you can offer him a little water when he's thirsty. Juice is okay at this point too — but no more than two to four ounces per day. (When you can, though, opt for fresh fruit over juice; it offers the same nutrients, plus fiber.)