Is there a cheat code for increasing influence?
Basically, head to the folder where the game's save files are stored (should be C:\Users\[username]\AppData\LocalLow\Glitch Pitch\Idol Manager\data), and open the save file you wish to edit with a text editor.
Then, look up "Rel_Influence_Points". There will be multiple of those (one for each idol). Find the one corresponding to the idol you wish to gain/lose influence on and just manually change the value on the string.