Before you do though, make sure you create a backup of all your production data, because it will be scrubbed when deleting your DigitalOcean droplet.
After you've backed up all your data, just run:
This will instruct DigitalOcean to shutdown and destroy your droplet, remove the
internal DNS entry associated with your server, as well as delete the
directory from your local working copy.
Your working copy will not be deleted by
sail destroy, you'll need to do this
manually if you wish. The
.backups directory will also not be affected and
will need to be deleted manually, if that's what you're after.