Cover the bottom of a large, heavy-bottomed pot with bacon and fry over medium-high heat. When it’s crispy, crumble the bacon in the pot. Add collards and fry in bacon grease for 15–30 seconds. Add enough water to cover greens, about 6 quarts. Stir in apple cider vinegar, oil, and honey. Simmer, uncovered, until liquid reduces significantly and greens are tender, about 2 hours. Add additional vinegar, honey, and salt, to taste.