In a small bowl, soak Italian bread in milk until soggy, about 5 minutes. Squeeze out excess milk and tear into small pieces. Combine bread with beef, chopped onion, Parmesan, chopped parsley, 1/4 teaspoon salt, and 1/4 teaspoon pepper. Shape into 1 inch balls.
Spray a skillet with cooking spray and heat over medium; drop in meatballs without over crowding pan. Cook for 6-8 minutes, turning to brown on all sides. Set aside and continue until all meatballs have been cooked. Toast hoagie rolls and spread with a thin layer of spaghetti sauce.
Assemble salad by tearing greens and adding to a large bowl. Toss together with olive oil, vinegar, and remaining 1/4 teaspoon of salt and pepper.
Add meatballs to rolls, and serve sandwiches with salad and sliced apples on the side.