Hirezake (hot sake [Japanese liquor] flavored with fish fins) is a way of drinking sake.
It is hot sake into which a grilled fin of an edible fish is put.
The representative hirezake is that with a blowfish fin. To make hirezake, you should at first grill the cut out fin until the surface is slightly burnt, then put it into a cup or something, and pour the hot sake on it. Then you should put a lid or something on the cup, and wait for the flavor to permeate into sake. The characteristic of hirezake is that the amber is clear even when it is stirred, they say. Some people kindle sake before drinking it.