German-Style Quick-Pickled Onions

6 calories; 0 g total fat; 0 g saturated fat; 0 g polyunsaturated fat; 0 g monounsaturated fat; 0 mg cholesterol; 37 mg sodium. 18 mg potassium; 1 g carbohydrates; 0 g fiber; 1 g sugar; 0 g protein; 0 g trans fatty acid; 1 IU vitamin a; 1 mg vitamin c; 0 mg thiamin; 0 mg riboflavin; 0 mg niacin equivalents; 0 mg vitamin b6; 2 mcg folate; 0 mcg vitamin b12; 3 mg calcium; 0 mg iron;