Keep 2 litre ice-cream containers or 1 litre yoghurt containers and fill them with left over food that you would give to your pets. When over half full, fill the tub with water to cover the food- don't fill all the way to the top, leave a couple of Cm's. 
Then put in the freezer overnight and the following day as it begins warm up, pop it out on the grass for your pets as a treat. You can use this for a lot of pets by just placing in the appropriate food for each animal.
This is great to keep them cool on a hot summers day and also great for dogs/cats that get bored and up to mischief if you are away at work for the day- you can pop it out just before you leave for work.
Make sure its in the shade and your pet will get hours of non stop licking fun and finding yummy treats as they go.
