Cook bacon as directed on package. Transfer to paper towels, let sit until cool enough to handle, then crumble and set aside. Discard bacon grease but do not wipe pan. Add olive oil and heat over medium low heat. Add onion and garlic then cook gently for 20 minutes, or until onion is very tender and golden. Preheat oven to 350 degrees. Add vinegar and sugar to onion then heat until simmering. Add spinach and heat through. Add cream cheese and cook gently until cream cheese melts. Stir in bacon crumbles and transfer to a pie dish then bake until bubbly, 5-10 minutes. Serve immediately with crackers or bread sticks. If you do not want to serve dip immediately, transfer to a small crock pot or fondue pot, to keep warm.