All of those "aquarium safe" glass cleaners work just as advertised, they're just too pricey for my tastes. Use anything you want, just apply it to a paper towel away from the tank and then rub it on. I clean the glass on my planted this way, and have never had a problem.
I also just use a damp cloth or paper towel. Even if you just spray windex on a cloth, you may get some on your hands and then accidentally get it in the tank. I am a little paranoid about that.