Interesting you propose the question this way. There are really two topics here. Saying things you mean. You could mean to tell the truth. You could mean to lie. The purpose of what you communicate is different than what you communicate. Drinking tends to allow ones emotions to spill out. If you have emotions you’re carrying around inside, there likely to come out when you’re drinking. You may end up saying something you’ve been holding inside for fear of the repercussions. But it’s the truth. You may desire to hurt somebody because you’ve been hurt. A common reaction when you get hurt is to intentionally inflict hurt on the person that hurt you. Even if it means spilling out ridiculous lies with the intent to hurt. Drinking in this case, may prevent you from controlling your emotions. You see, drinking has nothing to do with truth and lies. It has everything to do with emotional control. And for the record, it’s never OK to hurt someone just because you’ve been hurt. That usually involves doing and saying things you can’t take back.
Both. The truth is never so clear that it ever all comes out in one situation or another. If they say what they mean in one situation it also means there is something they aren't saying in the situation that they would in another. You have to piece them all together (contradictions and all) into one big picture.
They're less inhibited in what they might say, doesn't mean it's any more truthful than usual I reckon. Just gives you a better insight into what thoughts they have that they've never shared before, that can be good and bad.
"Vino veritas" as the Romans put it. But I'm not convinced. What someone says with alcohol's influence is certainly part of that person, but garbled, and not necessarily what they think or believe. 😀