A shower and bath combo. First, you take a normal warm bath. When you are ready, start draining the water but do not get out. Turn the shower on to it’s coldest, most frigid setting and remaining laying down in the tub. If you can survive after the water completely drains or 3 repeats of “Bulls on Parade” by Rage Against The Machine, you have successfully taken an Estonian shower.
Nothing wakes you up like a double espresso and an Estonian Shower