Heat the oven to 375°F. Line a small baking sheet with parchment paper.
In a large bowl, combine the grated apple, breadcrumbs, egg, milk, sage, salt, and black pepper. Stir until the breadcrumbs are evenly moistened.
Add the ground turkey. Mix gently with your hands or a fork just until combined. Avoid compacting the mixture, which can make the meatloaf dense.
Shape the mixture into a compact loaf on the prepared baking sheet.
In a small bowl, stir together the cranberry sauce, Dijon mustard, and apple cider vinegar. Spread about half of the glaze over the top of the loaf.
Bake until the center reaches 165°F on an instant-read thermometer, about 45 to 55 minutes. Spread the remaining glaze over the loaf during the last 10 minutes of baking.
Let the meatloaf rest for 10 minutes before slicing. This helps the tender slices hold their shape.