Which cocktail is made using bourbon and sweet vermouth?

The Manhattan is a classic cocktail that is specifically made by mixing bourbon and sweet vermouth, typically garnished with a cherry or a twist of lemon. The combination of these two ingredients creates a richly flavored drink that balances the sweetness of the vermouth with the boldness of the bourbon, making it a popular choice in cocktail culture.

In contrast, the Old Fashioned primarily features bourbon (or other whiskey) mixed with sugar, bitters, and a twist of citrus, but does not include sweet vermouth. The Mint Julep is primarily composed of bourbon, fresh mint, sugar, and crushed ice, also lacking sweet vermouth. Lastly, the Whiskey Sour features whiskey combined with lemon juice and sugar, typically topped with a cherry, but it does not involve sweet vermouth either. Thus, the Manhattan stands out as the only cocktail among the options listed that is defined by the use of bourbon and sweet vermouth.