datatables - sort icon duplicating

SB Admin theme includes Bootstrap add-on for DataTables.

However the code you've posted, includes default DataTables CSS. In this case, one or the other should be included.

The solution is to replace default DataTables CSS (//cdn.datatables.net/1.10.7/css/jquery.dataTables.css) with dataTables.bootstrap.css and add dataTables.bootstrap.min.js

If you prefer to use default DataTables CSS, then you need to fix sb-admin-2.css around lines 232-257 and remove rules related to table.dataTable.