In a large skillet over medium high heat brown bacon and render its fat. Add chopped greens to the pan in batches and turn until they wilt, then add more greens. When all of the greens are in the pan, add vinegar and cook a minute. Season greens with sugar and salt. Add chicken broth to the pan and cover. Reduce heat to medium low and simmer greens 15 to 20 minutes then serve.