How to stop Laravel 5 from caching configurations?

You can't stop the caching of config files since it doesn't happen automatically. The only thing you need to do, is not call config:cache.

The file itself can be found in bootstrap/cache/config.php.

Note that the location of the compiled config file has changed recently. Yours might also be in vendor/config.php or storage/framework/config.php. With a fresh install or if you run composer update the file should be in bootstrap/cache though.