Clean , fresh water should be available at all times. water should be changed every couple of hours.
would be 3 times ba day for a puppy
a better question is whats in your water that's giving your pups diarrhea? or it may not be the water, but something else.
The newborn puppies should be nursing from their mother, they get all the liquid they need from her the first two or three weeks.
About 4 weeks old put water in a bowl make sure you put your finger in it and make noise they sometimes can not see the water but are able to hear it or let them lick it off your finger.