没事用英语怎么说

"What do you use when you're not using anything?"

This is a simple and direct way to ask the question in English. The full sentence would be: "I'm wondering what you use when you're not using anything."

If you want a more concise answer, you can simply say: "What do you use when you're not using anything?" This is a common way to ask this question in English conversation, and it is clear and straightforward.