Most people connect choclate with our current blend of choclate and sugar. In its natural state, however, choclate is bitter rather than sweet (as anyone who's tried Mexican chicken mole can attest). Sugar was not native to the Americas but was brought in as a cash crop by the Europeans who had obtained it from Asia.
However, there is no doubt that the addictive qualities of choclate were prevalent in Mesoamerica.
Yeah, they used it to make a hot drink, a sort of unsweetened cocoa. Not much different in effect than hot coffee, another popular drink. To the world, the Americas contributed corn (maize), tomatos, peppers, potatoes, coffee, chocolate, and (on the darker side) tobacco, cocaine, and marijuana.