This is one of our favorite recipes for meatball subs. Get fresh rolls to load the meatballs up on that will also soak up a little of the marinara sauce.
Heat oil in a Dutch oven over medium. Add spinach and cook until wilted, about 2 minutes, stirring constantly.
Add garlic and cook for 30 seconds.
Add ¼ teaspoon salt and ¼ pepper. Drain well and finely chop spinach mixture.
Stir together ground turkey, sausage, breadcrumbs, Parmesan cheese, eggs, chopped spinach, and remaining ¼ teaspoon salt and pepper in a large bowl until well blended.
Add marinara and water to the Dutch oven and bring to a simmer over medium heat.
Form the turkey mixture into 1" balls add to the marinara sauce and cook for 10 minutes.
Reduce heat to medium-low and cover. Cook for 10 more minutes or until cooked through. Serve over hoagies and sprinkle with shredded cheese.