The b. a.c can rise significantly within ?
minutes after having a drink

According to ontrack.org, your blood reaches it's highest concentration 30-60 minutes after drinking before it begins to go down to it's normal level. This is different for each person because you have to take into account their body structure, their heart health, and other factors that can cause this to be faster or slower.

Because without physical activity, the body has extra "energy" if you will, and so when it is time for bed you are not tired, so you end up staying up all night. also there is probably an effect on your internal clock, which messes with your melatonin production which goes hand in hand with your sleep cycle