What fruit is typically used in a classic cosmopolitan cocktail?

In a classic cosmopolitan cocktail, lime is the fruit used primarily for its refreshing juice, which adds a distinct tartness that balances the sweetness of other ingredients like triple sec and cranberry juice. The acidity from fresh lime enhances the overall flavor profile, making the cocktail bright and invigorating.

While orange and lemon are popular in various cocktails, they are not the key citrus components of a cosmopolitan. The use of cherry is also common as a garnish in many drinks but does not play a significant role in the cosmopolitan's flavor, which is predominantly driven by lime. This characteristic makes lime an essential component of this iconic cocktail.