If you're in charge of caring for and feeding a litter of bouncy, cute and fluffy puppies, your main goal is essentially to create as comfortable, stable and healthy a growth environment as possible. Part of that involves always making sure that the little cuties drink and eat properly.
Puppies generally don't need to begin "drinking" anything on their own until they begin weaning, which in terms of a specific time frame, is up to a mother dog's judgment. Until a litter reaches about a month in age, the only thing they need to drink or eat in terms of nourishment and sustenance comes directly from Mommy. For wee puppies, a mother's milk is the beverage of choice. In cases of motherless litters, you can bottle-feed the youngsters powdered puppy formula using a puppy milk replacer. In these instances, the only necessary drink is formula.
When puppies hit the 8 week landmark, they're typically completely through with weaning. Since they're no longer getting their nutrition via nursing, the only thing they should be drinking is, pure and simple, water. The nutrient is key to ensuring a balanced and healthy canine diet, so make sure that puppies always have plenty of the clean, cool stuff within quick reach.
When puppies are around 3 weeks in age, you can begin to feed them solid food, or more specifically, dry food that is intended for puppy consumption. Make sure that the food is labelled as just for puppies, as the dietary needs of the young ones differ greatly from those of adult dogs. Puppies need more protein in their diets. Once puppies are ready to start eating solid foods, they're ready to begin drinking water. You don't have to wait until weaning is completely done to encourage this. Oftentimes puppies will emulate their mothers by drinking water.
Although young puppies do regularly consume their mother's dog milk until they're about 8 weeks old, milk from a cow is not a good idea for them. The ASPCA notes that cow's milk can cause uncomfortable gastrointestinal malaise in puppies, from diarrhea to tummy ache. Keep your puppies feeling good by never allowing them to drink milk from a cow, whether they're 8 weeks old or 6 months old.