Bring a large pot of water to boiling. Add the white vinegar to the water, then add the chicken tenderloins. Boil for 10 to 12 minutes, or until the chicken is cooked through. Remove and let cool slightly before shredding the chicken. Chill in the fridge for about 2 hours, before mixing with the yogurt sauce.
In a small bowl, mix together the yogurt, sliced grapes, chopped celery, chives, dill, garlic powder, onion powder, salt and pepper. Keep chilled until ready to mix with the chicken.
Combine the cooled, shredded chicken tenderloins with the yogurt sauce. Serve with crackers or on bread as a sandwich. Enjoy!