In a small mixing bowl, mix together the sour cream, mayonnaise, sugar, vinegar, salt, and pepper until smooth and creamy. Cover and refrigerate while you make the salad.
1/2 cup sour cream, 1/3 cup mayonnaise, 1 Tablespoon sugar, 2 teaspoons apple cider vinegar, 1/2 teaspoon salt, 1/2 teaspoon pepper