The judge made a judgement call in this case and was correct. Reasonable doubt.
However... It is quite possible to be drunk , sleep a few hours, and still be impaired. Car seats are not comfortable to sleep in. I bet that this guy would have woken up after a very few hours, depending on how drunk he was, and driven off in search of a Timmy's still impaired AND tired.
In fact many people driving to work on any given morning are impaired, but perhaps not drunk, from too short a time between their last drink and going to work even tho' they have slept.