
Kümmel is a sweet, colorless liqueur flavored mainly with caraway, plus fennel and anise.
Caraway is the flavor and it is rare in a bottle, so a rebuild adds ground caraway to an anise liqueur — the anise and fennel carry over, the caraway does not. Sweetness holds across the family.
Aquavit (akvavit)
Both take their main flavor from caraway seed, but aquavit is an unsweetened strong distillate where kümmel is a sweetened liqueur. Pour aquavit in its place and the drink comes out dry and sharp, and the sugar has to come back.
Its high sugar can precipitate into crystals that settle at the bottom of the bottle over time; gentle warming and shaking redissolves them.