You can more than likely go with a window film on your doors. 3M film will be expensive (you're paying for the name, and they outsource a LOT of their films). Look for dealers either through manufacturer websites or Google. Some high quality but less expensive options will be SunTek (
www.suntek.com) or Johnson (
www.johnsonwindowfilms.com). You can also check out Llumar (
www.llumar.com). They are pretty much the leader in window film technology.
A dual reflective film is probably the route you're looking to go, and most manufacturers will offer a warranty for seal failure and glass breakage. Check with your dealer. The job should cost less than $250, if you have a basic 2 car garage with 8 or less windows.
Gila is the cheap, low end brand made by CPFilms (Llumar's parent company) and I would recommend staying away from that brand.
If you're wondering, I used to install window film.
Tapatalk...my downtime occupier