I've visited Cuba this summer. As you may guess, I visited a few coffee plantations. Also, many famous coffee houses.
Before my visit, I thought that “Cuban coffee” is some kind of espresso with a little bit of sugar in it added during tamping. Thus, sugar is mixed during extraction as in Turkish coffee in brew time.
However, while was in Cuba I never ever experienced anybody added any bit of sugar in the grounds. So, I watched the whole set up carefully and realized that the sweetness in the Cuban coffee is not the result of the added sugar, but the over roasting of the coffee.
As far as I understood, the “Cuban coffee” is sweet as it is caramelized during the roasting process but not as a result of the added sugar. However, I would like to verify my observation with other coffee enthusiasts observations before finalizing my decision.
Therefore, the question could boil down to whether the Cuban coffee have additional sugar in it?