Bulk Delete Custom Entities (Not Entity Types)
You can  delete multiple entities using below API functions

entity_load


  Load entities from the database.
  
  The entities are stored in a static memory cache, and will not require
  database access if loaded again during the same page request.
  
  $entity_type: The entity type to load, e.g. node or user.
  
  $ids: An array of entity IDs, or FALSE to load all entities.


entity_delete_multiple


  Permanently delete multiple entities.


For Example to delete all node entities

&lt;?php
  $results = entity_load('node');
  $entity_ids = array_keys($results);
  entity_delete_multiple('node', $entity_ids);
  ?&gt;