Re-using k-cups can save money, as well as help the environment. After using a k-cup, give it time to cool down. Then, carefully remove the foil on top of the cup and dump out the grounds. Wash the k-cup out to try to get as many of the used grounds out as possible. Let the k-cup dry. Then, you can fill it with your own coffee grounds. Cover the cup tightly with plastic wrap. Try to cover the cup as tightly as possible so it doesn't leak. Remember, when you put the k-cup into the machine, to line up the bottom hole with the needle.
Each k-cup can be re-used 4 or 5 times.