I like to try to keep my cat's water chilled for a long time, so I take a plastic cereal bowl, fill it half-way with some warm tap water and put it in the freezer until it freezes solid. Then I run it under warm water to pop it out and put the ice block in a tin cat or dog dish that's a little bigger than the block of ice. I pour some water over it until the ice cracks, so they won't get scared, then fill it up with cold water. It stays colder longer!
