What is the simplest and fasted way to delete all records from a custom object? Do it from Developer Console by writing a few lines of Apex Code. Right? Well not really. To delete all records from a custom object, just navigate to the custom object definition, click on ‘Truncate’ and that’s it.
For the ‘Truncate’ option to show on custom object, do not forget to check ‘Enable Custom Object Truncate’ from Setup -> Customize -> User Interface as shown below