Not even a conspiracy theory. Before battles many different armies would take pills that were just speed called pervitin. The ones who started this practice were the germans. Hitler would take them, Himmler would take them, foot soldiers would take them, camp guards would take them. These drugs weren't used recreationally back then. They were used as performance enhancing drugs for soldiers that increase alertness. They really cause paranoia but I guess counts as being alert. This is backed up by a lot of legitimate studies and research. Holocaust denial is not.
https://time.com/5752114/nazi-military-drugs
https://www.history.com/news/inside-the-drug-use-that-fueled-nazi-germany