In the absence of a refrigerator, the "damp cloth" method is the most effective way to refresh a bottle of champagne. This method involves three simple steps that must be followed without omission. First, take a damp cloth and wring it out so that it is damp but not excessively watery. Next, wrap the Champagne bottle in the cloth. The last step is crucial, even if it may seem strange. The wrapped bottle must be placed in the sun. This process, known as thermodynamics, allows the sun's heat to evaporate the water contained in the cloth, while absorbing the heat from the Champagne bottle, allowing it to regain its freshness.