Aluminum Siding Hole Repair
Since you don't particularly care about looks, all you will need to do is create a patch out of aluminum sheet metal and attach it to the siding.

Start with a sheet of aluminum. A good source from this is from a roll of drip edge. Cut a square or rectangular piece out using tin snips, and make it slightly larger than the hole. You would want to make it large enough to cover it completely, and still have room to attach it.

Once the piece is cut, you should paint it to protect it, and have it blend in with the color of your siding. It doesn't need to be an exact match, but the closer, the better.

Attach the patch to the siding using 1/8" aluminum pop-rivets. You also should use a thin bead of caulk around the hole to keep it weather tight. Once the patch is installed, you should also apply one more coat of paint to cover up the heads of the rivets.