Why is this the answer?

The answer is gloves because this riddle is a creative language puzzle that makes you think about an everyday object in a surprising new way. Let's carefully examine the question: What do you fill with empty hands? Most of the time, when we hear the word "fill," we think about putting a substance like water, candy, or toys into an empty container. The riddle wants you to picture your bare, empty hands trying to put something into something else. It makes the task seem a little tricky at first. How can you fill anything if your hands are empty of what you need to fill it with? This is where the magic of the riddle works. The answer is not about what your hands are holding, but what your hands are actually *entering*. Think about a brand-new pair of gloves. Before you wear them, they are soft, flat, and often look a little floppy. Each glove has a hollow, empty space inside it. This space is shaped exactly like a hand with five fingers. It is an empty copy of your hand, waiting for the real one to arrive. When you slip your bare, or "empty," hands into the gloves, your hands are actually doing the filling. You are putting your own hands in to occupy the empty space in the fabric. Suddenly, the gloves are no longer flat. They become plump, shaped, and ready to work or keep you warm in the winter. You have filled the empty hand-shaped glove with your actual hand. It is a wonderful way of saying that the object you fill is designed to be filled by the exact same thing you use to fill it. The empty glove is filled by your empty hand. This clever twist is what makes "gloves" the correct and super fun answer to this puzzle.