As it may seem an easy thing to do, and to be honnest : it is, creating environment variables in your Homestead Virtual Machine is something you cannot find in the documentation.
While it is missing from the official Laravel Documentation, you can still find the info on a lost google page..
So today I'm saving you some trouble.
In order to add new environment variable in Laravel Homestead, simply add these lines in your Homestead.yaml file:
variables: - key: APP_ENV value: dev - key: SOME_KEY value: someValue - key: FOO value: bar
Of course, don't forget to run
vagrant reload --provision in order for your VM to be updated.