In a medium saucepan over medium-high heat, whisk together the maple syrup, thawed cherries, Dijon mustard, brown sugar, cinnamon and black pepper for about 5 minutes. Break up the cherries with the whisk to release some of the juice.
When the mixture starts to boil, add in the halved Brussels sprouts. Continue to cook until Brussels sprouts are tender, but still firm, about 10-12 minutes.
Remove from the heat. Drain the Brussels sprouts and allow them to sit until cool enough to handle.
Preheat the Indoor/Outdoor Grill on setting 4.
Place 1 halved Brussels sprout on a skewer followed by one slice of apple. Alternate until the skewer is full. Repeat with the remaining skewers.
Place the skewers on the preheated grill. Place the lid on the grill. Grill the skewers for 6 minutes per side. Serve immediately.