In any case, in order to sleep and earn money, you need to have a certain capital, or take care of a project or business that will generate profit without your intervention. In my opinion, the most suitable option is staking, but for this you need to first buy a sufficient amount of cryptocurrency, so that the profit is in the required amount.
Investment is the only way which can give you profit when you are sleeping because it increases in worth during favourable circumstances but the value of profit will depend on the amount you are using for investment.
If you are using money then your money will be increasing in value but it is not possible that without using money and working hard you will sleep and will become wealthy in just one night. In some cases you will just use your knowledge and money like investment in crypto and then leave it for appropriate timing then you will see that your invested amount has been increased if your coins remain profitable.