Yes, but why?
Mother's milk or properly mixed formular contains adequate amount of water (actually mostly water) so additional water is not really needed.
If child is vomitting/bad diarrhea
and you want to give fluid--pedialyte
is a good replacement. A small amount .1-2oz to wash out down the milk before bed or after baby food is not unreasonable.
Consult doc if you are unsure..