How can I prevent my swimming goggles from fogging up?

I'm not a serious swimmer, but I get annoyed when I swim and my goggles fog up. I usually just dip my goggles in the water and that fixes it for about 5 minutes, but then while I'm having fun, i have to pause, take my goggles off, then dip'em in the water. I don't have any anti fog oil or spray. Im looking for something quick that i can use that will really prevent the fog.