Cook tilapia in the microwave according to package directions. Break cooked fish into pieces. Lightly coat a panini press or griddle with cooking spray. Preheat panini press or griddle over medium heat.
On two slices of the bread, layer spinach, tomato, fish, and cheese. Top with the remaining two bread slices.
Place sandwiches in panini press. Cook about 3 minutes or until browned. (If using a griddle, place sandwiches on griddle. Weight sandwiches down with a heavy skillet [add food cans for more weight] and cook for 2 to 3 minutes or until bread is toasted. Turn sandwiches over, weight down, and cook about 2 minutes more or until browned.) Serve with Apple-Carrot Slaw.
In a small bowl stir together apple, carrot, Greek yogurt, and poppy seeds.