Please explain why does drinking beer the night before make my morning run easier?

No clue: And tens of thousands of amateur and professional coaches and sports medicine people would tell you that, if this is really true, that you are maybe the only one. Alcohol impairs exercise ability, particularly in large amounts, which is why athletes, for the most part, stay away from it before competitions. It damages muscle, depletes glycogen stores, and dehydrates us -none of which helps running.