Using Report Builder 3.0, this is a way to enable interactive sorting. This allows the viewer of the report to interactively sort columns either in ascending or descending order.
While in design mode, right-click the text box containing the column name and select “text box properties”. Once the property dialog window is open, click on “Interactive Sorting”. Place a check on “Enable Interactive Sorting on this text box”. Then select the column from the “Sort By’ drop-down field.