Dog diarrhea is caused by bacteria which penetrate into the body of the dogs mainly through the water drunk by the dogs. Hence it is wise to make sure that the water for drinking for your dog is kept fresh and healthy. This can be done by giving the dog mineral water from the same source of the water that you drink. However, if you consider it too expensive, you can boil some amount of water and store it in a jug or other place. When it is time for the dog to drink, then you should give it only the water that you had boiled before.