How should I monetize my game

Hello developers, I really need some ideas of how to monetize my game in a good way without making it annoying for players.

I’ve made a game called steal a bank to get some beans, basically it is a singleplayer stealth/FPS game with an online mode. The thing is, I’ve added gamepasses and a skin system for the online mode but no one buys them since the multiplayer is dead so I want you guys to give me some ideas on how to monetize it.

TL:DR I’m not making cash because all the monetization went to a multiplayer no one plays, how can I make cash with a singleplayer mode.

Game Link:

Get a YouTuber to play it. Maybe egtv, dantdm, or flamingo?

I suggest having a few cool guns that are locked behind a paywall.

Don’t make them give too much of an advantage though, make it something like a freeze ray or a teleporting gun that deals a bit more extra damage and of course has a special ability along with it.

Or make gamepasses which give you a special movement ability such as climbing

Or even something such as pets.

Basically try to think of any cool game mechanic/features and incorporate them into the game so that they don’t give a ridiculous amount of power, but are just cool and useful.