The sweetener is a solid block of unrefined boiled-down cane juice, not table sugar — vendors dissolve it whole in water before adding the lime.
Papelón con limón is made by dissolving papelón — a solid brown block of unrefined cane sugar — in water, then adding fresh lime juice and ice. It's sold from stands and juice carts across Venezuela alongside arepas and empanadas, a cheap, tart-sweet cooldown from the heat.