Cold apple + warm caramel = joy. Room-temp apple + warm caramel = a slip-fest. The cold apple shocks the caramel into clinging tight, like a koala to its mama.
But if your caramel is too hot? It will melt your apple’s skin, creating a watery layer between fruit and candy. You want the caramel around 100°F (juice-feel-warm, not scalding).