I do the milk jugs or any other jug I can find filled with water & stash all over the house. We are on a private well & if the power goes out, we have no water. I also keep plastic pop bottles frozen to put in lunch boxes. When we had our Ferrets, (they loved to travel with us), I would keep a frozen pop bottle in their cage with a wash cloth around it to keep them cooled down. They loved laying against it. This works with any animal. In the hot part of the summer, it is good to do this for your outside dogs.