In a heavy saucepan, melt the butter/margarine. Add onions and cook until
they are golden, do not brown. Add the undiluted beef broth, 1 soup can of
water, Coca-Cola, salt, vinegar, and pepper. Cover and simmer 20 to 25
minutes.

In a broiler, toast one side of the French bread slices. Turn and
generously sprinkle with the Parmesan cheese. Toast until browned. Into
deep bowls, ladle the soup and top with the toast, cheese-sided up. Makes 4
servings or about 6 cups.
Recipe: "International Cooking with Coca-Cola", a give-away
pamphlet from The Coca-Cola Company, 1981