My crazy ex-gf once well asleep at the wheel of my car (borrowed) right in the middle of a busy intersection (alcohol, pot, and probably a cocktail of some other shit). The cops woke her up, and her brief, polite, near 0.03 bac infused explanation to cops was basically "my friend volunteered to drive since I'm shitfaced drunk, and she fucked off somewhere, where is she now well i don't remember, why am I behind the wheel don't remember guess I wanted to turn on the heater or something, whats her name i don't remember which one of them, by all respect officer i don't feel i'm in a condition to discuss legally significant matters right now, if I'm detained would you please notify my attorney". In the drunk tank she went, and in the end they didn't even seriously try to indict her on anything.
Now where I live you're not quilty of DWI until the wheels start turning, whether you have the engine running or not (pretty common this side of the pond, actually). And IDK how it works in US exactly, also the Wendy's probably had a camer pointed at the drivethrough etc, but I ASSume if he just got out of the car initially and said he is in no condition to move it, he could have had it plea bargained down to pretty much nothing given the circumstances.