>>or even being asleep in the car while drunk.
If the keys are in the ignition, you are DUI.[0]
Even sleeping in the car is also considered a DUI in some states[1]. Beware!
[0] http://caselaw.findlaw.com/co-supreme-court/1006683.html
[1] http://blogs.findlaw.com/blotter/2015/07/how-to-sleep-it-off...