Place sauerkraut in a colander and rinse with cold water. Drain well, using a spoon to press out excess liquid. Set aside.
Lightly coat one side of each bread slice with cooking spray. Place four bread slices, coated sides down, on a work surface. Top with chicken, sauerkraut, apple slices, and cheese. Top with the remaining four bread slices, coated sides up.
Coat an unheated grill pan or large skillet with cooking spray. Preheat over medium-low heat for 1 to 2 minutes. Add sandwiches, in batches if necessary. Place a heavy skillet atop sandwiches. Cook over medium-low heat for 6 to 8 minutes or until bottoms are toasted. Using hot pads, carefully remove top skillet. Turn sandwiches and top again with skillet. Cook for 6 to 8 minutes more or until bottoms are toasted.
1 starch, 4 lean meat, 1 fat