How can we bubble sort a table data in PL/SQL?

This index, is it the primary key you're referring to by any chance. If that's the case, you're on the wrong track. It should never be changed, in fact it should never be visible to the user.
If it's just an ordering you want you can add that with ROW_NUMBER( ) OVER (ORDER BY Data) as Index
If you want help with the query then update your question using the Improve Question button to the right and add your current query you need help with.

If you mean that you want to store the data in order, you can't do it. You can not guarantee that the database inserts in order in ordered blocks, nor that it reads the blocks in order.
Well, that last part isn't entirely true, If you store your data in an Index Organized Table, you're actually storing your data in an actual index and it will be sorted by default. (Note, not stored in order, but read in order)

If you want to sort the data you've fetched in a query using your own stored procedure you can of course do that, but it will certainly be magnitudes slower.

All of this is by the way part of Chris Dates definition of the First Normal Form. http://en.wikipedia.org/wiki/First_normal_form#1NF_tables_as_representations_of_relations

You still haven't said what problem you're trying to solve. :-)