i just found this glitch so im not to sure what all to do you, this is just what i did. also this makes you only invisible in you car but you can drive through all cars in the game
1.get any car impounded (i used zentorno)
2.hop the wall at the impound lot and switch hats
3.run to your car and at the bottom right corner you should see a spinning orange circle
4.after the circle goes away get in car and disconnect router,ethernet cable,wireless adapter,ect
5.will spawn you in single player as soon as you can hold down on d-pad switch to online character
6.you should spawn driving your car out of the impound lot and invisible you will be able to see your player but others will not