On the menu screen (where you get to pick a 1 or 2 player game, tournament or options) hold the joystick in port 1 to the right and the joystick in port 0 to the left for about five seconds. The screen will fade out and a cheat options menu will appear. You can now set player 1 and 2 to be the evil Max, enable infinite credits, toggle the CPU as player 2 and enable infinite energy.
If the characters have shadows beneath them whilst playing, then you’ve got a copy of the enhanced version. Hold the joystick in port 1 down, until the cheat options appear.
Note that port 1 is the standard port for one player games and port 0 is the mouse port.