As someone who doesn’t drink or tend to hang around people who do, I don’t tend to think about this all that much, but here are my thoughts upon reading the question:
No alcohol at all seems a bit severe, and ill defined–what counts as “before”? Obviously that drink you have in 1999 doesn’t count now. And surely you can consume at least very small quantities, like in wine tasting or eating food that still has some leftover alcohol in it.
But going by feeling seems obviously bad to me, for two reasons. First, how drunk you currently are is less important than how drunk you are at the end. So it has to be anticipatory, not based on current anything. But the bigger issue is that people seem to be bad at judging exactly how inebriated they are.
I could almost go with the third option, since it’s more concrete. But I feel like going up to the legal limit is too far. You want to be well below something like that, below the point where it would affect your driving at all. I’m sure the law tries to be conservative with its limits, to cover lower tolerances to alcohol, but, still, going right up to the line seems fraught with potential issues to me.
To me, it’s just “are you in any way inebriated”? But that has to be judged accurately, erring on the side of caution.
BTW, when I was a kid, I actually imagined it meant drinking alcohol in the car, or just before getting in. To my kid brain, “and” implied “at the same time.” So, to this day, that is my initial interpretation in the split second before the rest of my brain kicks in.