Pruno, or prison wine, is an alcoholic beverage variously made from apples, oranges, fruit cocktail, fruit juices, hard candy, sugar, high fructose syrup, and possibly other ingredients, including crumbled bread. Bread supposedly provides the yeast for the pruno to ferment. Pruno originated in (and remains largely confined to) prisons, where it can be produced with the limited selection of equipment and ingredients available to inmates. The concoction can be made using only a plastic bag, hot running water, and a towel or sock to conceal the pulp during fermentation. The end result has been colorfully described as a "bile flavored wine-cooler". Depending on the time spent fermenting (always balanced against the risk of discovery by officers), the sugar content, and the quality of the ingredients and preparation, pruno's alcohol content by volume can range from as low as 2% (equivalent to a very weak beer) to as high as 14% (equivalent to a strong wine).
A prune is a dried plum, most commonly from the European plum (Prunus domestica). Not all plum species or varieties can be dried into prunes. A prune is the firm-fleshed fruit (plum) of Prunus domestica varieties that have a high soluble solids content, and does not ferment during drying. Use of the term "prune" for fresh plums is obsolete except when applied to varieties of plum grown for drying.