Preheat your campfire or grill to medium heat.
In a bowl, toss the sliced apples with lemon juice, cinnamon, and brown sugar until well coated.
Lay a sheet of aluminum foil on a flat surface.
Place a quarter of the apple mixture in the center of the foil.
Top with a tablespoon of granola or crushed graham crackers, a few mini marshmallows, and a couple of pieces of butter.
Fold the foil over the filling to create a sealed packet, making sure there are no openings.
Repeat with the remaining ingredients to create three more packets.
Place the packets on the grill or over the campfire, cooking for about 15-20 minutes, turning occasionally.
Carefully open the packets (steam will escape) and drizzle with caramel sauce if desired.
Serve warm.