01 - In a medium bowl, whisk together the maple syrup, Dijon mustard, olive oil, apple cider vinegar, minced garlic, thyme, salt, and pepper until fully combined and smooth.
02 - Place the chicken breasts in a large resealable plastic bag or shallow dish. Pour the marinade over the chicken, ensuring each piece is evenly coated. Seal or cover tightly and refrigerate for at least 1 hour, or up to 8 hours for deeper flavor.
03 - Preheat grill to medium-high heat (approximately 375–400°F). Lightly oil the grill grates to prevent sticking.
04 - Remove the chicken from the marinade, allowing excess to drip off. Discard any remaining marinade. Place chicken on the grill and cook for 6–8 minutes per side, depending on thickness, until the internal temperature reaches 165°F and the exterior is golden with distinct grill marks.
05 - Transfer the grilled chicken to a cutting board and rest for 5 minutes to allow juices to redistribute. Garnish with fresh thyme sprigs if desired and serve immediately.