Drug Wars - The Stash | Grand Theft Auto 4: The Ballad of Gay Tony
The drugs will be marked on your radar at the start of the scenario. It’s usually in a lot, surrounded by rival gang members. Pick them off from afar with a Sniper Rifle or drive in and gun them down from inside your car. Clear the way, grab the drugs (or just grab the drugs and make a run for it), and make your way to the drop off.
This video is from our unofficial game guide. You can view the full guide here