There is two type of sparkling sake:

1. Forced into carbon dioxide when sake bottling
It is generally used for low alcohol sake. When the sake is diluted with water to bottling concentration, carbon dioxide is injected into the liquor. After 10 days of low-temperature storage, carbon dioxide dissolves in the liquor and bubbles are generated when the bottle is opened.

2. Secondary fermentation in the bottle
Like the champagne production method, carbon dioxide is produced through secondary fermentation in the bottle. This type of sake would not pasteurization after bottling, and fermentation is continued in the bottle.