And at the same time you can lose everything during sleep. There are plenty of ways to earn money without having to make a lot of effort; another question is to choose the paths that are most effective and not too risky for the wallet. Perhaps now the best way is to invest one of the many icos and wait for a miracle in the future.
i think the most efficient way to make money while you sleep is to invest your money to profitable project in order to gain profit.