Which ingredient is NOT found in a Dirty Martini?

A Dirty Martini is a variation of the classic Martini, characterized by the addition of olive brine, which gives it a distinct salty flavor. The traditional components of a Martini include gin and dry vermouth, which serve as the base of the drink. The inclusion of olive brine in a Dirty Martini distinguishes it from the standard recipe.

Sweet vermouth, on the other hand, is typically used in other cocktails such as the Manhattan or the Rob Roy, but it is not an ingredient in a Dirty Martini. While dry vermouth and gin are essential components of both a regular and a Dirty Martini, sweet vermouth does not contribute to the flavor profile that defines a Dirty Martini. This is why it is the ingredient that is not found in this particular cocktail.