When army eating, one shovels food into their mouth as fast as they can, sometimes chewing once or twice before swallowing, so they can be done earlier than everyone else, so they can tend to other more fun activities. This often happens in the army, hence "army eat". When army eating, it takes an average of 3-4 minutes to eat a regular meal.
Dude, the sarge wants us out training in 5 minutes! We'd better army eat!