What are best anti-fog staff to keep glasses from fogging up?

[Autryville]

My glasses always get fogging up during cold mornings, I want to know what are best anti-fog staff to keep glasses from fogging up?

[Auvergne]

The most useful anti-fog spray I have ever used is Itech Fog Free Spray. It is easy-to-use, clear, odorless, easy-to-apply, dries-in-a-jiffy and can last quite a long time.

[Auxvasse]

I have been using cat crap for years and that is the only thing that keeps my glasses fog free in the worst conditions. But in most time you can only get it online.