Note: This is for the Gay Tony version.

Do a drug war with Henrique and Armando, and there will be one drug war where the drugs are stashed in a car, which is the Sultan RS.

Kill all of the enemies and drop off the drugs. Then use the health cheat code if the car is a little damaged.

After that drive it to the parking space at your safehouse and save the game.

Your Sultan RS car will be waiting outside your safehouse.