什么在里面?
里面 is pronounced really strangely here
If you hover over "is" it will never offer "有".
Thats because the sentence roughly translates as: "Inside have what?" To my understanding
里面是什么?
That is kind of a direct English translation: "Inside is what? (What is inside?)" just the order is changed. But in Chinese it is the presence of something or the state of having something: so we use only “有” or “在” to describe the situation.