What are the ingredients for a Gibson cocktail?

The Gibson cocktail is characterized by a combination of dry vermouth and gin, typically garnished with a pickled onion. This signature garnish is what distinguishes the Gibson from other gin-based cocktails, such as the classic martini, which is generally garnished with an olive or a lemon twist. The use of dry vermouth enhances the overall flavor profile of the gin, making it a crisp and refreshing drink.

The other options do not align with the traditional preparation of a Gibson. For instance, using gin with a lemon twist is more representative of a martini. Vodka and tonic water is a completely different cocktail altogether, and sweet vermouth with whiskey refers to a different category of drinks, such as a Manhattan. Thus, the combination of dry vermouth, gin, and an onion garnish is what accurately defines a Gibson cocktail.