To bring back its sparkle, all you need to do is drop a single raisin into the bottle just moments before pouring yourself a glass, The Sun reports. The reason it works is all down to carbon dioxide, which is what gives drinks like champagne its wonderful bubbles.
It will be flat and the fine fruit aromas will have faded, replaced by the smell of vinegar. It will taste sour and altogether unpleasant. The only thing bad champagne is good for is pouring down the drain—you wouldn't even want to cook with it by this point.