You can earn free coins by using specific software, visiting websites, completing tasks, helping scientists (!), playing CS:GO, watching ads, etc.
I compiled a short list of my favourite ways to earn free coins on the internet.
BAT - Basic Attention Token
Brave is a free and open-source web browser developed by Brave Software, Inc. based on the Chromium web browser. By using Brave, you can win free $BAT, just by letting the browser show you some random ads while navigating. The payout is made monthly, and you need at least 25BAT to withdraw (if you don't fund your wallet, of course).
Billed as "digital money for the modern world," Nano is a lightweight cryptocurrency that is designed to facilitate secure, practically instant payments, without fees, and addresses some of the major limitations of both legacy financial infrastructure, and many modern cryptocurrencies.
There's several games and ways to win nano, including Quake and CS:GO, compiled in one great website: https://earn-nano.com/
PRE - Presearch
Presearch aims to build a next-generation search engine that is powered by its community. Presearch funds operations through what it describes as a 'transparent, unobtrusive advertising system' that enables advertisers and users to stake PRE on keywords. By doing so, they get to display advertisements on those keywords in the search results.
You'll win $PRE just by using presearch as the default search engine in your browser. Combined with Brave, you'll be winning two different crypto coins just by browsing the web.
BAN - Banano
Banano is distributed in a free and fair way through airdrops, contests, giveways, tipbots/competitions and faucet games. Most giveaways are taking place in the Discord Channel, but also in our other social channels. Keep an eye on current announcements.
With Banano Miner, instead of running arbitrary calculations to "mine" a cryptocurrency, your computer runs protein fold simulations through Folding@Home to help scientists around the world fight diseases such as Alzheimers, Cancer, Parkinson's. As a result of your contribution, you get rewarded in Banano.
CURE - Curecoin
Curecoin describes itself as a cryptographic utility token dedicated to replacing ASIC mining with protein folding computations - helping scientists find new medicines in lieu of mining hashes. Curecoin's goal is to accelerate research in the medical sciences relating to Cancer, Alzheimer's, Antibiotics, Diabetes, Huntington's, Ebola, Zika, HIV, Parkinson's, repurposing drug compounds, and Astrobiology.
Like Banano Miner, the Curecoin system leverages Stanford's* Folding@home distributed research software. As of 1 May 2019, Curecoin's folding team is ranked #1 on the global Folding@home network. Development is focused on faster transactions, increased security, collaboration with science blockchain consortium partners (like FoldingCoin), as well as supporting philanthropic projects through the Curecoin Project's 501c3 sponsor (Vision's Made Viable).
That's it (for now)!
I'll add more ways to win as I find them in the future, so bookmark it!