It might be best to not assume people are familiar enough with the game, from context it seems to be some kind of alternative money/experience made so you only earn it in multiplayer, and a search would bear that out ( http://www.gamezone.com/originals/a-beginner-s-guide-to-final-fantasy-type-0-hd-jsux
) but still best not to assume such things.
Is there a cheat for it?
There are two main ways I would approach it
1) Like a ROM hack port of a cheat.
2) Game mission level.
1) is a minor variation on the classic thing people use to teach basic assembly hacking. Here you would tack on an instruction to add so many SPP around the same time they are giving you gold (gil?), experience or whatever else. It might not display it on screen though. If you want to get really fancy you could make it a slightly more random reward as well.
2) game mission level is in the mission structure within the level is probably going to be a reward. I would not be surprised to see it SPP just be an item available for reward like any other, but not used as normal rewards. You figure out the reward list for missions and the value SPP uses and add that in. It should display such things on screen.
The proper proper method would probably be something similar to what you say and somewhere in the code there would be something like if in multiplayer then reward SPP, if using academy backup party members then don't. Figuring out this could be more annoying though.