Add onions to a medium-sized bowl. In a small saucepan, add vinegar, sugar and salt. Bring to a boil then pour over the onions. Toss to combine then let sit and cool for at least 15 minutes. Store leftovers, covered, in the refrigerator for 1 week.
In a large skillet over medium-high heat, add turkey then cook and crumble until browned. Add ginger, salt, crushed red pepper flakes and bell pepper. Stir and cook until bell pepper softens. Add garlic, coleslaw, sesame oil, soy sauce, honey, lime juice and cilantro. Stir until combined then remove from heat.
Add meat mixture to lettuce leaves and garnish with pickled onions, Thai sweet chili sauce, peanuts and cilantro.
Notes
If using extra lean ground turkey, olive oil may need to be added to keep moist while browning.