You can try Azure Functions for free by accessing the link: Try Azure Functions
It will open the following page:
For this trial, you can create your functions using C# or JavaScript, however Azure Functions also supports F#, Node.js, Python, PHP, batch, bash, or any executable.
After selection the scenario and the programming language, it will ask you to authenticate using one of the following authentication providers:
Once authenticated, you'll receive a sandbox environment that offers a similar experience to that of the Azure Portal. You will have access to this sandbox environment for one hour: