Which ingredient is NOT a part of the Tom Collins recipe?

The Tom Collins is a classic cocktail that typically includes specific ingredients necessary for its preparation. The key components of a Tom Collins are gin, sweet and sour mix (often referred to as sweet and sour or sour mix), club soda, and sometimes a garnish like a cherry or a lemon slice.

In this context, the correct choice identifies that "Cuba lime" is not an ingredient in the Tom Collins recipe. Instead, the cocktail relies on the balanced sourness from the sweet and sour mix along with the refreshing effervescence from the club soda. The use of grenadine is not characteristic of a Tom Collins either, as it would introduce sweetness and color that are not typical in this drink.

Choosing the correct ingredient that does not belong in the Tom Collins highlights the understanding of traditional cocktail recipes and ensures clarity in drink preparation, as the integrity of the cocktail's taste is dependent on including the right ingredients.