Which ingredient is not included in the preparation of a Tall peppermint mocha?

The preparation of a Tall peppermint mocha includes espresso, peppermint syrup, and mocha sauce, which are essential components that contribute to its signature flavor profile. Espresso serves as the base, providing a rich, bold coffee flavor. Peppermint syrup adds a refreshing minty essence that's characteristic of this beverage, while mocha sauce introduces a layer of chocolate sweetness that complements the other flavors perfectly.

Vanilla syrup is not a typical ingredient in a peppermint mocha. Its absence helps to maintain the distinct mint and chocolate flavors without the additional complexity or sweetness that vanilla would introduce. Therefore, the correct answer is the ingredient that does not belong in the standard recipe for this coffee drink.