Add rolled oats, milk, Greek yogurt, maple syrup, chia seeds, vanilla extract, and sea salt to a jar or airtight container.
Stir everything together until fully combined.
Seal the container with a lid and place in the refrigerator overnight.
For quicker soaking, refrigerate for at least 2–4 hours.
The next morning, stir the Best Overnight Oats well.
If the mixture is too thick, add a splash of milk until your desired consistency is reached.
Add toppings and enjoy straight from the jar or transfer to a bowl.