Wash the apples. Peel and core them, then cut them into cubes or chunks.
Add the cubed apples to the slow cooker.
Pour in the water, apple juice, or apple cider.
Add the lemon juice, cinnamon, salt, sugar, and vanilla. Stir gently to combine.
Cover and cook on LOW for 4–6 hours or HIGH for 2–3 hours, or until the apples are very soft and tender.
Stir the apples well. For chunky applesauce, mash the apples with a potato masher. For smooth applesauce, blend with an immersion blender until smooth.
Serve warm or allow the applesauce to cool before refrigerating.