Sake is essentially rice. So
there are many variations of rice flavors from sweet to steamed to burnt, etc. But we also have the yeasty conversion of a glucose into alcohol so sake has many "sweet" elements, which I like to say are fruity tones instead of sweet.
For premium sake, at least 30 percent of the grain has usually been polished away, while the rice for the following high-end types of sake need to be polished even more: Ginjo (吟醸) - at least 40 percent of the grain has been polished away. Daiginjo (大吟醸) - at least 50 percent of the grain has been polished away.