You need to remember that hot chocolate from today has nothing to do with ancient Mexican cocoa. Most reports say that the drink was extremely bitter and spicy. As sugar is native to the old world. Which leads to the belief that they added chili and pure ground cocoa powder to water and drank that. Chili and cocoa both have health benefits having trace caffeine, some vitamins/minerals, and huge amounts of antioxidants so it can't had been that bad for him.

As to the quantity you stated though. That is probably exaggerated as a status symbol. The cacao plant was semi sacred and held and really high esteem by ancient mesoamericans. Some accounts even have it compared to currency as it's value was so high. So displaying that he had the wealth to drink so much of such a valuable commodity was probably a prestige propaganda thing. Probably similar to a Medieval European Monarch showing off his wealth by having fancy spices imported from India at his feast.