1. Create a Final Episode/Secret Episode save but do not open it.
2. Start a new Aqua game and play until the Jaq forced fight. DO NOT SAVE at any point.
3. Make sure Jaq dies fast.
4. Once you fail the fight load the Final Episode/Secret Episode Save. (You can technically do this in any forced fight except orbs, Jaq is just recommended because he is the first, so the fastest.)

Video showing how to do it: (Footage is from a psp so only the final episode save file is showcased but it works exactly the same way with the secret episode)