Here is a goal: How to make overnight oats?

Which way makes more sense to accomplish this goal?

Choose from:
(a). In a mason jar, add in oats, fruit and then pour over cold milk and place the jar with the lid off in the freezer overnight, in the morning you can shake the jar and eat the oats.
(b). In a mason jar, add in oats, fruit and then pour over cold milk and place the jar with the lid on in the fridge overnight, in the morning you can shake the jar and eat the oats.
(b).