No way, José! According to historians, ancient Romans drank a concoction of wine, sugar, and water. So that's likely where the tradition of adding sugar to sangria originated (but their wine probably tasted awful). With the modern marvel that is 21st Century winemaking, you don't need to add sugar for a great sangria. And actually, I believe sangria is more flavorful and authentic with just a little or no sugar at all. Too much can mask the nuance in the wine, brandy, and fruit. Leaving the sugar out also allows those on a low-carb or ketogenic diet to partake in a glass.