This is a 100% SOLO Method
Store any non-blacklisted vehicle in your garage SOLO after patch 1.13. This includes supercars and friend's cars - no police, military, or commercial vehicles. This glitch is a little tricky, so watch the video to get an example of the timing.
Park the vehicle you wanna store in front of your garage(if solo, preferably in a non-despawning location).
Enter your garage and get in the car you want to replace (If this car is insured, then the other will be)
Hold Down on the D-Pad & choose a character.
Press O/B to back out as soon as the black alert screen appears.
Do steps 3 & 4 several times to get down a a good speed of doing it.
Press R2/RT and quickly repeat steps 3 & 4.
If the glitch worked, you should be able to drive in your garage.
Press Start, Online > Jobs > Join Job > Join Random Race and press X/A.
Once the job screen begins to load, keep pressing O/B then X/A to quit the job quickly.
You will spawn glitched back in your garage.
Run out, get in the car, wait, you will glitch out, then drive out of the garage. Done.
**If you drive out of your garage while trying, just drive back in and try again.
**If you get frozen in your garage and can't do anything, switch session, and try again.
Credit goes to rafaelrgc on Se7ensins for the original tutorial.