The Frankfurt Sour is a twist on the classic Whiskey Sour, with a local touch. It combines bourbon whiskey, fresh lemon juice, simple syrup, and a splash of apple cider. The cocktail is shaken with ice and strained into a rocks glass, garnished with a lemon twist. The Frankfurt Sour is a refreshing and tangy cocktail that perfectly balances the sweetness of the bourbon with the tartness of the lemon juice. It's a must-try for whiskey lovers visiting Frankfurt.