The only way you can probably make money while sleeping is if you are a business man who owns chains of businesses, and have a lot of employees who handle affairs in your absence.
If you're to apply that with trading, that will be trading via bot, automated system that trades for you.
But you mustn't have to make it sound a rosy, in all the examples I've given above, you don't only money while sleeping, but you can also lose money, there are two sides to the coin, and it's more risky when you trade with a bot