firstly reinstalling the bash-completion package with:

sudo apt-get install –reinstall bash-completion

Then backing up your .bashrc file:

mv ~/.bashrc ~/.bashrc.bak

Finally, replace your .bashrc file with the default from /etc/skel/.bashrc by using:

cp /etc/skel/.bashrc ~/

This will ensure the following ‘complete’ config is restored within the file:

logout and back in should be working fine even with sudo tab completion