Hello, sir, this cannot be smaller, this is the most suitable size for a person's health because an adult needs at least 3 liters a day, and a child needs 1 liter. She needs to drink 5/2 liters of water, so if you buy a height for your daughter (God forgive me), you can fill it with clean, beautiful, healthy water from home and then there is no need to refill it from another place. (And my personal advice is, do not buy a black thermos for your beautiful daughter, we have white and red, it would suit her better. good day Sir .