Remember that they will need food and water just like you and you may not be able to run to your neighborhood grocery store. If they have no food or water, they will either die or you will become closer than you wished for. Remember that male cats can develop FUS from dry food and big dogs can have deadly problems with their stomach from eating or drinking large amounts in the heat. Cats are desert animals and don't drink a LOT of water, but they need it available at all times. Unlike a dog, when a cat pants, it is in trouble.
Milk can cause terrible diarrhea in many pets.
There are some bottled drinks for pets you can buy, but old fashioned water is the best thing for all of us. Prevent tragic problems by discussing what your pets can and cannot torerate with your vet. If you are fortunate enough to keep your pets with you, please remember that they will be firghtened and uneasy and may try to run away. It is, therefore a very good idea to have some means of restraining them to keep them from harm. If you are able to stay in your own home, wonderful, but always have an alternative.