Which ingredient is NOT found in a standard Margarita?

A standard Margarita is composed primarily of three key ingredients: tequila, lime juice, and a sweetener like triple sec. The combination of these ingredients creates the classic flavor profile associated with Margaritas. Lime juice contributes acidity and freshness, tequila is the base spirit providing the primary flavor, and triple sec adds sweetness and depth.

Cranberry juice, while it may be present in a variation of cocktails, is not an ingredient typically used in a standard Margarita. This drink is characterized by its tangy and refreshing profile, which would be altered by the addition of cranberry juice, making it less about the Mexican origins of the Margarita and more like a different mixed drink altogether. Therefore, cranberry juice rightly stands out as the ingredient that does not belong in a standard Margarita.