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