Let's assume that you are still at the stage of quick learning, when you don't speak Japanese fluently yet.
And you decide to go drinking with your Japanese friends and you chat the whole night and OH!...Unfortunately you happen to drink too much and the next day you don't remember anything about what happened last night.

It makes me think that if you can't remember the last night, then perhaps all the conversation progress was useless. Unless you will make progress somehow subliminally, which is questionable...

This makes me come to a conclusion that from a language learners perspective it's better to use as little alcohol as possible when speaking to the people of your target language as it seems that alcohol is the enemy of memorizing.
But I don't know, what about a beer or two?

I don't know about you but I have to drink a lot to get memory loss and drinking that much is best avoided for many reasons :$

There is probably an optimum number of beers where confidence and wanting to talk about anything to anybody are high, yet memory loss is still at zero... just have to remember to stop at that point

A few beers to loosen the tongue is never a bad thing

If you don't remember that you spoke in Japanese...

How do you know you spoke in Japanese?

Somehow, I don't think you're gonna get together with Japanese friends and drink alcohol while learning the fine nuances of the language...