Sunglasses / Fog

Do you use any fog spray for your riding glasses? If so; what kind do like? Does it actually work?

I use "Cat Crap" honest, that's the name. REI carries it. It's the best I've found.... also advertised for ski goggles etc.

Here's a pic of the product. It's small and easy to carry on rides, but I honestly don't need to apply it very often.

I second the use of cat crap for glasses, inside of car windows ( a little goes a long way), bathroom mirrors, scuba masks etc.

+ 3 on the little red container...

But if it's super cold, there's nothing that really keeps the fog off my regular Smith sunglasses, so when I commute below 15F or so I use ski goggles, which looks crazy but works phenomenally.

Is that stuff safe for prescription lenses? I have prescription Transitions lenses in my Oakleys and I don't want to risk ruining them or voiding the "warranty" on them. They're the only Rx sunglasses I have since I dropped my Spy and scratched the new lenses in those.