Fill a mason jar halfway with hot cereal. Stir in chia seeds, brown sugar and cinnamon.
Spoon almond butter and vanilla on top. Fill to the top with almond milk. Stir gently. Add more almond milk until jar is full and mixture is soupy and well combined. Cover and refrigerate at least 8 hours or overnight.
Remove lid and stir in 1-2 tablespoons almond milk. Add freshly cut apple and garnish with more brown sugar and chia seeds.
If desired, microwave in 20-second intervals until heated through, stirring in between.