The skyfall cheat in GTA 5 is an interesting one, and can often be given to other gamers as a practical joke... You see what it does is spawn you in mid-air, free-falling. So yup, unless you have a parachute you're pretty much screwed!
There is another tactic that you might be able to use to survive though — simply press forward on the left analog stick (or your keyboard) and try to land head first into a wall or the ground. That doesn't make sense we know, but try it and you might survive the skyfall cheat!
