https://www.npr.org/sections/health-shots/2017/03/07/518986612/author-says-hitler-was-blitzed-on-cocaine-and-opiates-during-the-war

Opiates and cocaine. Sounds bad but (apparently I need to defend Hitler and prove my critics totally right) keep in mind that we took some time to really understand how bad all these drugs were. Sigmund Freud died in 1939 right before he started using and before he realized how dangerous it was and recanted he wrote a book called "on cocaine" which  basically talks about how much he loved cocaine.

Also, "German supersoldier serum" was just methamphetamine, which powered the long journeys of the blitzkrieg. It wasn't until much later that it was really appreciated how dangerous drugs are.

https://time.com/5752114/nazi-military-drugs/