:) get one of those painting pans the ones for the long paint rollers. They slope down so they can be deep and shallow, perfect for filling a bit with cool water and tossing in some frozen peas and carrots :) they love peas but you may have to clean up the pea skins! they usually peel them.

Find a natural yogurt with i believe 5 grams of sugar or lower and toss it in the freezer then let it become a sort of slush and the ratties can have a cool snack :) remember not to put to much in yogurt is a treat!