Every army did that as soon as amphetamines were discovered. They still do. The upside is enormous for the average person trying to stay alive without food.

I read that the difference between the British amphetamines and the German meth played a role in North Africa. Basically the British version didn’t last as long, which actually gave them an advantage because they could sleep.

In North Africa it’s so hot that you can’t do anything during the afternoon so the British could sleep a bit after fighting all morning. The German version lasted 12 hours, so if they took it at 5 AM, they were awake until 5 PM. By 5 PM the British were done with their nap and could attack the tired Germans again (who had to take more meth).