Chocolate was, apparently, always a thing for the military. There was Pervitin laced into pralinés dubbed "Hausfrauenschokolade" (housewife chocolate), and it was also mixed into chocolate bars as "Panzerschokolade" (tank chocolate). And in case you are wondering now what that Pervitin brand name stands for - it's meth. (Yeah.)
A different kind of chocolate, also for military use, but not used as a drug delivery agent, was the D ration chocolate bar. That is, well, mostly harmless or so it seems, and if you are intrigued now, Tasting History has a podcast about it: