The diehard way to lose game:

- Play friendly to tire your players before competitive match.
- Name the worst performing guy (from recent form) who don't have the highest quality in team as captain.
- Change your tactic to hard attacking with forced counterattack.
- Shuffle your lineup so that everyone is out of position. You can save orders so that this is done and revert back with a click of a button.


Sit back and enjoy
You can lose like 0:10 even against a subpar team.

The morale penalty will be a disaster, though.