Distribution

General
Sell 50 "Ice-Creams" around town, they aren't really ice creams, yes they are drugs. Takes a while but it's worth it.

Walkthrough
Drive around town with the truck siren on (L3). Stop at regular intervals. When you stop, wait for a bit and people with pink arrows over their head should run up to the truck if you are close enough to them. If not, then a message will pop up saying that there aren't any customers in that area. It will take a while if there aren't alot of people. Make sure you haven't activated the "Pedestrians Riot" cheat because then everyone fights and no one will walk up to the truck. I found that there are lots of people at intersections off the highway, if that helps.