This shows how to get into's trevor's meth lab which you can't really get into without trying.
1) Go to Sandy Shores
2) Get your car and pull up next to the convenient store which is on my screen
3) Brake the window
4) Climb up on the left heater then into the window
5) Have someone place a bounty on you and have fun killing
Note: Cops can enter the building somehow so be careful.