The reason it's said that dogs can't drink tap water is due to the chlorine and other possible contaminants and fluoride that can be in city tap water.
However dogs can drink tap water and many dogs have survived on tap water for years without any issues.
Unless your dog has sensitivities to the chlorine or fluoride in the tap water, then your dog can safely drink tap water.
Bottled water is not always better for your dog although bottled water is filtered and purified.
Most bottled water goes through filtration and purification processes, which remove harmful contaminants like parasites and bacteria as well as heavy metals.
However dogs can also drink tap water from the faucet without any issues city tap water contains chlorine, which some dogs may be sensitive too.
But if your dog is not sensitive to the chlorine in tap water the dog can safely drink tap water.
Even well water is okay for dogs to drink just like it's okay for humans to drink.
If the dog is sensitive to the chlorine in tap water, then the bottled water can be better for your dog.
Otherwise it's an unnecessary expense to purchase bottled water for your dog and the tap water will hydrate your dog just as good and be just as good for your dogs health.
Dogs should not drink flavored water or mineral enhanced water as they can contain additives that can be harmful to dogs.
And ensure the dog is drinking fresh and cool water which goes for the bottled water and the city tap water as well.
Dogs should always have access to fresh and cool water at all times so the dog can drink the water when they're thirsty.
Bottled water is basically tap water that has gone through a filtered process and purification process in a bottled water factor and other than that the bottled water is the same as city tap water.
Most bottled water plants get the water they bottle from a city supply, like you get through your home and then they filter and purify it and make huge profits on the bottled water.