Imagine biting into a blazing hot jawbreaker. It seems like it would only split slightly and sting your mouth. But jawbreakers contain many sugar layers, and when heat travels through the candy, the outside cools while the center begins to boil. That creates massive pressure inside. The second you bite, the shell cracks open and all that pressure escapes, spraying molten sugar everywhere and leaving you and anyone nearby with painful burns in just a split second. Way worse than you'd expect.