A dash was an informal measurement used in cooking.
Beverly Crusher ordered warm milk with a dash of nutmeg for Jean-Luc Picard to help him sleep. (TNG: "All Good Things...")
A dash of ice salt was part of a recipe shared by Gideon Seyetik in 2370. (DS9: "Second Sight")
A Klingon martini contained vermouth, gin, and a dash of bloodwine. (VOY: "In the Flesh")