Masternodes with regular ROI or staking. But make sure the project is alive and with a good roadmap.
If your goal is to earn a passive income, there are lots of potential ICO that you can invest. You only have to make a research every ICO and look that is suit you and applicable to your budget. Just be careful of a scam ICO and you don't have to rush to earn immediately with your investment. It takes time to get the result you want.