I don't understand why do you want that. But I gues the easiest way to achieve that is just to wet the glas from outside with hard water. The stains will take away the glare. Or you buy antireflection foil.
You're better off treating the light sources rather than the tanks but that may be difficult for a number of reasons. Any film you apply - spray will be way too inconsistent - is going to drastically reduce what you can see in the aquarium.
I don't understand why do you want that. But I gues the easiest way to achieve that is just to wet the glas from outside with hard water. The stains will take away the glare. Or you buy antireflection foil.