It took me many goes to finish Sydney. This is the actual town of Sydney, not the area. It requires a lot of coffee to complete.
I failed it about 4 times. During the first goes I hadn't written the no big trucks code so I could still bring large trucks (> 40 tonnes) right into the middle of Sydney, and I still failed it. The town would consume all the coffee before the truck could go back to the plantation and bring the next load. I knew there must be a better way of completing it, so I didn't change the difficulty of this one.
I tried a couple of other strategies, and also had to replenish the supply of coffee, requiring a lot of fertilizer. Each failed, but got me a bit closer. I found overloading storage helped a lot.
In the end I did a quick mental calc to best guess how much Sydney would consume during the time it would take me to deliver, from as close as I could get, using the biggest trucks I could use and prepared that much excess before even starting again.
I did it with four trucks in the end. Most of my fail attempts only used three trucks. I did use some "bonuses" to help me out.
Anyway, I don't want to give too much away and let you figure it out. Just don't start this one until you have a good idea on playing the game.
Now off to try some other tough ones.