Our iLumen8 UV Shooting and Blacklight glasses are specifically designed to help eliminate fogging (by increasing airflow to the lens area), especially in active sports.
But not all glasses are designed that way, so you can buy anti-fog spray products for lenses to help this problem. However you may consider saving your money, and employ a 'do it yourself' method using dishwashing soap.
Check out this short YouTube video, it shows you exactly how to do this :
Its a handy and inexpensive tip, and the application should last for at least a few sessions outside. Let us know how it works for you!