Eggshells, lime peels, potato shavings, and yogurt bacteria cultures may seem more detritus than delicious, but they are several of many ingredients in a fermented Guyanese beverage known as Sweet Potato Fly. The drink is traditionally enjoyed as a health tonic, but in some households it’s regarded as a seasonal beverage and a nonalcoholic stand-in for eggnog.
Beyond the base of sugar and sweet potato, flavoring agents vary by recipe. Popular add-ins include ginger, nutmeg, cinnamon, and various citrus fruits. The yogurt can also be swapped out for other active bacteria cultures such as water kefir or ginger bug. But every variety is consistent on two points: tubers and fermentation. Once the initial labor-intensive grating, zesting, and mixing process is complete, the container is set aside for two to three days to give a chance for the bacteria to feast on the eggshells and sugar, and provide the amalgam with its bubbly zip. The result is a like a cold, fizzy wassail.