I need help with a metaphor! Right now! Please!?

I have a paper I wrote and I'm suppose to have a metaphor in it. I thought that " Who needs sleep like a camle needs water" was a metaphor. But I guess its not. HOw can I turn that into a metaphor. Is as thirsty as a camel a metaphor? HOw about as tired as a sloth. or something like that, But the thing is it has to start with who needs sleep. Please help!