This is a special thing that lives in Australia. And not just Aussie, it was born and bred in South Australia. You can get this wonderful version of iced coffee in other states, but generally you have to be close to the border, which is an issue for Tasmanians. They don't have borders down there.
It's been around since 1977, and since it thrived in SA, getting awards at the shows and milk drink competitions it was in, it spread across the island. Everyone loves it, and people can quote "It's Farmer's Union or it's nothing" and still be understood. Many shops sell perhaps a dozen or so of the other brands, such as Dare, which had the clever ad campaign of "Dare to leave the Union", but it probably didn't affect too many people, as dozens upon dozens of the white, brown and teal cartons line the rows in the cooled section.
Farmers Union comes in several sizes. There's the baby version which is 375mL, the real man's version of 600mL, the 750 mL Stubby version in a plastic bottle, and the family version comes in three sizes: 1, 2, and 3 liter containers. It also comes in different variations. There's "Feel Good", which is the less-fat version, and then three different strengths of the coffee itself. There is light, regular and strong. Don't buy light. Go buy yourself milk if you're really this weak. Though the only difference is meant to be the sugar level, everyone knows Zero Coke doesn't taste as good as the real deal. If you buy strong you can convince yourself that you made yourself a coffee and added lots of milk. It tastes that real.
Don't let the idea of a carton put you off. Drinking from a carton is not a bad experience, and I can barely grasp your dislike for it. Indeed, Farmers Union Iced Coffee outsells the great Coke itself in South Australia. In 2002 over 22 million liters of this stuff was bought. No, the sun has not deranged us. It is, to quote common drinkers of the beverage, "bloody awesome" and an "amazing experience that must be repeated".
When you come here, buy it. You must. This along with Vegemite and Tim Tams and the kangaroos are the prime reason people even come to this bloody red dust bowl.