Actually, my impression is that the main driver of that "alcohol free beer taste" is the absence of the taste of alcohol. I kind of want to test this hypthesis by adding pure alcohol to an alcohol free beer, but pure alcohol is not really something you find in the supermarket. Germany has a non-alcoholic drink called "Malzbier" (malt beer), which is basically the liquid you would ferment to make beer. It is _insanely_ sweet. So I would expect that a lightly fermented beer would be much closer to a sweet drink than to what we expect under the name "beer".