I have never heard of feeding it sugar. I don't think that's a very good idea, because it would produce more yeast production than is advisable. I just use plain, raw milk. A lot of people use pasteurized, but I like the thicker consistency you get with raw.
Anyway, the way I like it is to pour it into the blender and start whizzing. Then, add frozen mango chunk in the chute until the consistency is like a milk shake - you know, thick and kind of grainy. It is wonderful and you don't have to add any sugar, since the mango sweetens it enough.
You can do this with other fruits, as well, but most I add stevia with...