In a separate bowl, combine all the ingredients including the drained relish. If the tartar sauce is too thick, stir in a teaspoon or two of the reserved liquid until it reaches your desired consistency.
1 cup mayonnaise, 1 tablespoon fresh dill, 1 tablespoon freshly squeezed lemon juice, 1 teaspoon horseradish, 1 teaspoon granulated sugar, ¼ teaspoon black pepper