Sour Apple Mix is a popular cocktail ingredient used primarily to impart a tart, crisp apple flavor to drinks. It's often used in fruity and sweet cocktails, such as the Sour Apple Martini, which is known for its bright green color and sharp apple taste. This mix typically combines sour apple flavoring with a sweetener, making it a convenient way to add a distinct apple note and a balanced sourness, which can cut through the sweetness of other cocktail ingredients.