What unique ingredient is placed in a Champagne Cocktail along with sugar?

In a Champagne Cocktail, the unique ingredient placed along with sugar is bitters. Specifically, Angostura bitters are commonly used to enhance the flavor profile of the cocktail. The combination of sugar and bitters adds depth and complexity to the drink, complementing the effervescence of the Champagne. When the sugar is soaked with bitters and then topped with Champagne, it creates a refreshing cocktail with a balance of sweet and bitter notes, elevating the drinking experience. This classic preparation is rooted in traditional cocktail-making, where bitters were used not only for flavor but also for their medicinal properties.

Other ingredients listed, such as grenadine, peach schnapps, and mint leaves, do not traditionally belong in a Champagne Cocktail and would significantly alter its intended flavor profile. Grenadine would introduce sweetness and color, peach schnapps would lend a fruity essence, and mint leaves, while aromatic, are not part of this specific cocktail's recipe. Each of these alternatives changes the character of the drink, moving it away from the classic Champagne Cocktail.