They recommend cleaning the glass mat with regular alcohol and hand sanitizer for stickier messes.
It's also a good idea to clean it once in a while with some Expo Dry Erase Surface Cleaner, after you've degunked it with regular cleaning. Yes, it has alcohol in it to clean but it also has a conditioner in it to help the protect the glass. Over time, white boards can get dried out with over use. I used to have one in my classroom that could only be cleaned with a Comet style bathroom cleaner. Not good.
They also have other Expo Whiteboard Care like a 3 step process for white boards if you really want to pamper your glass mat.
Try it once and you'll be sure to notice the difference.