I did something once & almost learned the hard way. I'll NEVER do it again.
I was with a group of friends at a restaurant/bar. One woman in the group was a heavy drinker. Since I rarely drink, I don't have much knowledge about alcohol content. I counted 11 times the waiter brought her drinks that I later learned were "Brandy." I saw how little of it was in the bottom of each big glass, so i didn't think she was drinking much.
When we got up to leave around 1:00am, I saw that she was stumbling & having trouble walking & talking. Since I've seen what drunk drivers can do, I told her I would drive her home & take her to the parking lot tomorrow to get her car.