Okay, I found the solution, there is a way to have fields associated to entities without bundles. You use the same name for bundle as entity. Fortunately, I was also able to use entity reference field. Sharing my experience with everyone -- http://www.innoraft.com/blog/use-entity-reference-your-custom-entities-without-bundles
Hi Guys,Entities seem to be the biggest problem of my life for the past few weeks :-)Ok, so I have an entity without any bundles. I read this in hook_entity_info that bundles are not necessary.This entry can be omitted if this entity type exposes a single bundle (all entities have the same collection of fields). The name of this single bundle will be the same as the entity type.Now, I need to attach fields to my entity. I use field_create_field for my entity reference field which seems to work fine. When I attach this field to my instance using field_create_instance, I see an error saying:drupal FieldException: Attempt to create an instance of field without a bundleDoes this mean I cannot attach fields to entities which do not have bundles?--
Cheers,Mukesh Agarwal________________________________Innoraft Solutions || +91 8017220799