When you havent had anything to drink, but you're acting in a way that makes you look completely smashed. When a girl, typically named Ttephanie is completely sober, but is acting so ridiculous that her friends say she's Sober Drunk.
friend: Ttephanie, Why are you dancing on that table? You havent had anything to drink!
A driver who is so bad and/or douche that every time he or she gets behind the wheel, they might as well have had 6 shots of jager.
"Ever had a friend who's such a shitty driver you wouldn't let them driving sober?"
"Yeah man sober drunk drivers are douchebags, and a menace to society!"