Momokawa sake makes a bunch: asian pear, yuzu, ginger, hazelnut, and some berry flavored one. I think the problem with infusing sake is that the alcohol content's pretty low, so you'd probably have to use 1) lots of the flavorant, or 2) steep it for a while, like more than a week. I don't know if sake goes bad if you leave it unrefrigerated after opening, but if you keep it in the fridge the infusion will take even longer.........