What happens when you delete a Clustered index and Non Clustered Index once created
From MSDN:


  When a clustered index is dropped, the data rows that were stored in
  the leaf level of the clustered index are stored in an unordered table
  (heap). Dropping a clustered index can take time because in addition
  to dropping the clustered index, all nonclustered indexes on the table
  must be rebuilt to replace the clustered index keys with row pointers
  to the heap. When you drop all indexes on a table, drop the
  nonclustered indexes first and the clustered index last. That way, no
  indexes have to be rebuilt.


https://technet.microsoft.com/en-us/library/ms190691(v=sql.105).aspx

As for the nonclustered index drops, they aren't DELETING any data, it's a metadata operation and the index pages are simply deallocated. Think about TRUNCATE versus DELETE, TRUNCATE just deallocates the pages and you're done.  Dropping a nonclustered index is very similar, hence why dropping one is lightning fast when you do it (unless you are blocked).