I think you are referring to hibiscus drink. This drink is served relatively across the world with different methods of preparation and can be served hot or cold. While sometimes, it is used as a herbal medicinal drink like in tea, other times it is prepared with a lot of flavors, sugars and additives like in soft drinks.
It is made from the sepals of the Roselle flower. it contains vitamin c, minerals, citric acid, tartaric acid, some polysaccharides and it has 37 calories per 100g of serving. It has a distinct darker magenta color.
In my country, it is popularly served cold by boiling the dried sepals with ginger, clove, pineapples and any desired flavor. Sugar is added for taste and kept to chill. In my opinion though, too much additives tend to dilute it's health benefits.