The war, on drugs.

During WW2 German troops were issued with a substance called Pervitin. It was essentially methamphetamine, more commonly known as Meth today, and was an essential part of the Blitzkrieg doctrine - allowing tankers and storm troopers to function for protracted periods of time, increasing concentration and focus.

Pervitin was sometimes called "Panzerschokolade" or "Tank Driver's Chocolate". The premium consumable used by German tank drivers to increase their focus and concentration? Chocolate.

TL;DR - E25 drivers are on Meth.