Only time can lower your blood alcohol concentration; exercise, sauna or coffee does not make any difference.

Driving when you are tired is comparative to driving under the influence of alcohol; your ability to concentrate and react is adversely affected, leading to poor judgement.

Reaction/thinking time is usually about 0.5 - 2 seconds, but factors such as poor visibility, too many sensory inputs, problems concentrating or use of certain medications or intoxicants may significantly increase this.