heroku delete app code example
Example 1: remove heroku remote
git remote rm heroku
Example 2: heroku cli delete app
$ heroku apps:destroy [YOUR-APP-HERE]
Example 3: heroku delete app
heroku apps:destroy <app_name>
Example 4: turn off heroku app
From The Heroku Webpage
Dashboard => Your App Name => Resources => Pencil icon=> Flip the switch => Confirm