Doppio and Fermented Tea are produced all around the globe. And they change according to region in where they are cultivated. So, the question arises what is Doppio and Fermented Tea's differentiating factor?In following section we will take a close look at what is Doppio and Fermented Tea color, serving style, types and much more. First thing to know is what are the different types of Doppio and Fermented Tea. Well, Doppio types include Espresso while types of Fermented Tea are Oolong, Black, Pu-erh.