Which ingredient is used to muddle in the Old Fashion cocktail?

In an Old Fashioned cocktail, the muddling process is primarily associated with sugar. Traditionally, a sugar cube is placed in the bottom of the glass, and it is muddled with a small amount of water and bitters. This creates a sweet base that complements the whiskey used in the drink. The purpose of muddling the sugar is to dissolve it, ensuring that the sweetness is evenly distributed throughout the cocktail.

While fruit – particularly orange or cherries – can be added to the drink, and bitters is an essential flavoring component, neither of these is the main ingredient that is muddled to create the foundation of the cocktail. Club soda is not typically involved in an Old Fashioned at all, as this cocktail is served neat, without soda or dilution in its basic form. Thus, the focus on sugar as the ingredient used in the muddling process makes this the correct choice for the Old Fashioned cocktail preparation.