One sure way to earn bitcoin withoutinvestment is to use what is called a faucet site.
Bitcoin faucets give a little bit of digital currency every so often, normally once an hour or once every thirty minutes.
All you do is sign up to the faucet and then you can collect from the faucet, normally once per hour.
The amount you can collect for free is small, but over days of time, and by using multiple faucets, you can save up a bigger amount.
Most faucet sites also include other ways to earn bitcoin, like completing surveys, playing games, and watching videos.
With a combination of collecting from the faucet and doing offers you can earn a good amount of bitcoin over time without any financial investment.
A list of the best bitcoin and altcoin faucets