Crisp and juicy pieces of slab bacon and just the right hit of red wine vinegar bring the perfect tangy-porky balance to these slow-cooked Southern greens.
Cook bacon in a large wide pot over medium heat, stirring occasionally, until golden and crisp, about 15 minutes. Add onion, reduce heat to medium-low, and cook, stirring occasionally, until onion is softened and lightly golden, about 5 minutes. Add garlic and cook 1 minute.
Add collard greens. Increase heat to high and cook, stirring occasionally, until just wilted, about 8 minutes. Add vinegar and cook, stirring frequently, until liquid is almost evaporated, 5–7 minutes. Stir in sugar and 6 cups water; bring to a boil, then reduce heat to low and simmer until collard greens are tender, about 1 hour. Transfer to a platter and season with salt.
Collard greens can be cooked 2 days ahead; cover and chill. Warm in a covered large wide pot with 1–2 Tbsp. water over medium heat, about 8–10 minutes, just before serving.
