Preheat your campfire or grill to medium heat.
In a mixing bowl, combine the sliced apples, lemon juice, cinnamon, brown sugar, flour, and vanilla extract. Mix well until the apples are evenly coated.
Lay a piece of aluminum foil on a flat surface. Place a quarter of the apple mixture in the center of the foil.
Top with a quarter of the granola or crushed graham crackers and a few mini marshmallows.
Fold the foil over the apple mixture to create a sealed packet, ensuring there are no openings for the juices to escape.
Repeat this process for the remaining apple mixture and ingredients.
Place the packets on the grill or campfire grate, cooking for about 15-20 minutes, turning occasionally, until the apples are tender and the mixture is bubbly.
Carefully remove the packets from the heat and let them cool for a minute.
Open the packets and drizzle with caramel sauce if desired. Serve warm.