When I want a little sweet treat I make smoothies.
My base is always frozen banana + milk + oats then do one of these:
Cinnamon + vanilla
Pumpkin + pumpkin spice+ brown sugar
Strawberries/blue berries
Cost like under a dollar to make a good cup and they are pretty filling.
Toast with butter and brown sugar. Super cheap, super good, and basically ingredients almost every household has.