Apple cake will stay fresh for up to 3-5 days, depending on how you store it. Once baked, apple cake can be kept in a cool place at room temperature, provided it's not extremely hot where you are. To store at room temperature, place the apple cake in an airtight container in a cool place, away from moisture. The cake will stay fresh for up to 3 days. Alternatively, you can store it in the fridge for up to 5 days.