We (Army National Guard) use Break Free and whateever cleaning rods and brushes we can scrounge. It's almost impossible to get a complete rod assembled. We also have a very limited amount of Otis kits. What I do with my troops is we take our rifles and the crap the supply nazi grudgingly loans us into a classroom at the armory, Then I break out my own cleaning supplies, including bore snakes, break parts cleaner, Sweets, and other items, and pass them around. We go outside to use the potent stuff. The guys in the motor pool use the parts washer on their rifles. A SGT takes care of his troops.
I have my personal GI kit and an Otis kit that I use when I'm cleaning my own M16 alone.
But, the official answer to your question is: The Army uses Break Free and the issue cleaning kits to maintain their rifles.