Boy I wish I'd thought of this. The guy who first thought of the idea should be given an award for originality!!!

Cut off the top and part of the neck from a plastic bottle, as shown in the image to the left.

Insert a plastic bag thru the neck opening, and use the cap to screw it shut for an air and water tight seal! This is a great idea to share. Good for us and the environment too.

Here's the post on LifeHacker. That site has a lot of great tips!