Milk Is Not Recommended
Many dogs lack the proper enzymes to break down lactose, the sugar in milk. Lactose intolerant people also lack these same enzymes. Without the presence of enzymes to break down lactose, it remains undigested and ferments in the intestine. This causes diarrhea and an upset stomach. If your dog appears to be able to tolerate milk, a cup as a treat every so often will do no harm. Milk with the lactose removed would be the best choice as a treat. Milk should never be used as a primary fluid for a dog.
Gatorade Contains Too Much Sugar
Any drink with vitamin or mineral supplements for humans could be harmful to a dog. Dogs can tolerate only specific amounts of certain vitamins and minerals that already naturally occur in dog food and water. Gatorade also contains a high percentage of sugar which could be very harmful to a diabetic dog. There are also artificial colorings and additives which can disrupt the healthy functioning of the urinary tract and other systems.
Whole Fruit Is Better Than Fruit Juice
Whole juice is not as good as fresh water. Dogs can drink fresh fruit juice in small quantities including apple juice and orange juice. Any fruit juice for a dog should be free of added sugar, artificial colors, or other ingredients. It would be a much better idea to give your dog a piece of fresh apple than to risk a juice that isn't really just juice. Even too much fresh juice can put too much sugar into your dog's diet. Most high quality dog foods already contain some fruit for your dog's best nutrition.
Pool Water Contains Harmful Chemicals
Do not let your dog drink from chlorinated pools. Pool water contains a high level of a variety of chemicals such as chlorine. When a dog drinks pool water, he or she ingests more chlorine than is healthy and might also be ingesting other chemicals. There also might be algae, insects, bacteria growth, and other harmful substances in the pool. A small sip of pool water will not put your dog in the emergency vet's office.
Toilet Bowls Contain Bacteria
Even the cleanest water becomes unsafe for dogs to drink if its container is dirty. Toilet bowls can contain many harmful types of organisms and bacteria. A toilet bowl may also contain chemicals used for cleaning which can be harmful to dogs.
Water From Puddles and Ponds Contains Parasites
Water from puddles and ponds can contain bacteria, parasites, and viruses that form from the lack of the water's movement. A fungal infection can grow due to pathogens that are present in still water molds and fungi. The organisms that live in the water molds can be harmful to a dog's digestion.