'Torrefacto' refers to a coffee blend produced from beans that have been glazed with sugar before roasting. This was originally done as a way to sneakily add weight to the beans, but has become popular in some parts of the world, e.g. Spain, France, Portugal, Costa Rica, and Argentina.
Torrefacto coffee is generally a mix of 20-30% torrefacto beans, with the rest being regular beans (some mixes will go as high as 80% torrefacto). The resulting coffee is dark, bitter, and acidic. Some people report finding it sweet, possibly because of the taste of the caramelization (although the sugar is blackened beyond the point where it is at all akin to candy), and possibly because they are likely to drink it in an espresso drink, such as café con leche.
At least one study has found that torrefacto coffee has higher levels of antioxidants, particularly when brewed in an espresso machine or moka pot. This has resulted in a minor upsurge in popularity, although in America it remains very much a speciality coffee.
I have only had the Nestle brand Torrefacto mix, containing 30% caramelized beans. In my limited experience, it is not sweet at all, being dark and bitter, but perhaps having a slight caramel taste when served with lots of milk and sugar.
In Spanish, torrefacto means 'high-roast', although it originates from the Latin torrefacere meaning 'to roast' or 'to scorch'; this in turn comes from the Latin torris, meaning 'firebrand' and facere meaning 'to do/ or 'to make'.
Thanks to andycyca for help with the etymology.