Why do you wake up early after drinking alcohol?

as you drink alcohol, you increase your blood sugar levels, as you sleep, this sugar level drops. The adrenal glands kick in when your blood sugar drops and wake you up. Sometimes, if you eat something with carbohydrates or sugar (i.e. a sandwich or warm milk with sugar or honey) the body gets the sugar it needs, the adrenaline goes down, you relax and then can go back to sleep.