Here's a working high jump glitch for GTA V Online. Take note that this might get remove by Rockstar when they update the game with a new patch but at the meantime, it is still usable and you can do this glitch right after you've read this article.
[It apparently works on xbox one, however possibly not working on PS4]
1 - Find a wall low enough to walk over without jumping. 2 - Position a bike as show in one of the videos below parallel to the wall you are jumping over.
3 - Be in first person, and holding a pistol.
4 - Sprint at the wall. Get it right and you go flying into the air.
You take very little fall damage too, even after going higher than buildings and falling back to the ground. If you land on a vehicle however, it may hurt! :P
Videos showing it in action:
Crane jump with bike
Friend finding multiple other places you can do the glitch - Mangedamn
Similar jump without a bike
Friend who originally found the glitch - Kizzer69
Credits: [Glitch] High jump glitch by FlickOrz