You can substitute mustard or turnip greens for the collards; reduce their boiling time to 2 minutes.
Bring 4 quarts water to boil in large pot. Stir in 1 tablespoon salt, then add collard greens, 1 handful at a time. Cook until tender, about 5 minutes. Drain collards in colander and rinse with cold water until greens are cool, about 1 minute. Drain, pressing greens with rubber spatula to release excess liquid.
Place greens on clean kitchen towel and compress into 10-inch log. Roll up towel tightly and squeeze over sink to release excess liquid. Remove greens from towel and cut crosswise into ¼-inch slices.
Cook bacon in 12-inch nonstick skillet over medium heat until crisp, 6 to 8 minutes. Increase heat to medium-high, stir in greens, and cook, stirring frequently, until lightly browned, 3 to 4 minutes. Stir in garlic and cook until greens are spotty brown, 1 to 2 minutes. Stir in vinegar and cook until liquid evaporates, about 30 seconds. Season with salt and pepper to taste. Serve, passing extra vinegar separately.
