Add the milk, oats, yogurt, applesauce, chia seeds, cinnamon, and maple syrup (and protein powder, if desired) to a jar or container with a lid. Mix or shake well until fully combined.

Refrigerate overnight, or for at least 3 hours (or see recipe notes for quick version). Stir and add a little more milk, if you like them thinner.

Top with freshly diced apples, granola, and a sprinkle of cinnamon just before eating, if desired.