>>50323575There's very little lore you can actually work with in pokemon, like biology etc, they are just magical beasts.
If I had to give a fake biology reason to why they can do it.
Appletun's crust is hardened syrup that is produced in excess. The large bulbous shape is actually like a frog's Vocal sack, that over time can fill with a sweet but acidic liquid used to attract prey.
When full it will excrete the excess fluid from the top of it's back, giving off an alluring smell to attract targets or mates. On exposure to air the syrup rapidly becomes non acidic and safe to eat. This effect is faster in cold weather so Many trainers leave appletun to cool on window shelves.
