Your child: Why can I have only one glass of apple juice?
You: Because we will eat dinner soon, I don’t want you to spoil your appetite!
Your child: Why does apple juice spoil my appetite?
You: Because it's filling and it has a lot of sugar!
Your child: Why can't I have sugar?
You: Because it will make you more thirsty and it's not good for your teeth!
Your child: Why is sugar not good for my teeth?
You: Eating sugar attracts bacteria and they make holes in your teeth!
Your child: Why do bacteria make holes in my teeth?