Heat oven to 500 degrees F.
Mix together onion, chili sauce, water, vinegar and sugar in small bowl. Spread in the middle of a 14 x 14-inch square of heavy-duty aluminum foil. Bring 2 opposite sides of foil up; fold edges together 3 times. Repeat with other 2 sides, folding to make packet.
Bake in 500 degree oven 30 minutes. Carefully unwrap and serve hot with hot dogs and hamburgers.
