Use

# /etc/init.d/apache2 restart

OR

$ sudo /etc/init.d/apache2 restart

OR

$ sudo service apache2 restart

OR

simply create an alias for the command that works for you.

alias rsws='/etc/init.d/apache2 restart'

Using my alias ‘rswd’

$ rsws
[ ok ] Restarting apache2 (via systemctl): apache2.service.