Assuming that "the one made at my favorite cafe" is not an acceptable response, the answer varies depending on where you consider within the country. Different brands of commercial Iced Coffee have different distribution areas, and dramatic regional variations as to which is the most popular.
"Iced coffee has been sold commercially in Australia since the late 19th century in the form of a syrup, an example of which is Bushells Coffe and Chickory Essence, and more recently as a prepackaged, ready to consume drink.
One popular brand is Farmers Union Iced Coffee, which outsells Coca Cola in South Australia and has become an official icon and legend in that state. This particular brand is now widely available in Queensland (as far north as Mackay), Northern Territory, Victoria, New South Wales and Tasmania. The product is not yet available in Western Australia.
Pauls Iced Coffee is the second most popular drink in the Northern Territory, after beer. It is not available outside of the Northern Territory, save for rare instances when it is sold in Dili, East Timor.
Other varieties include Big M, Ice Break, Brownes Iced Coffee Chill, Brownes Coffee Chill, Brownes Dome Cappucino Supershake, Brownes Mocha Chill, Dare, Masters Espresso, Masters Iced Coffee and Max Iced Coffee."
I must say that I have seen few of these brands in my suburb!
https://en.wikipedia.org/wiki/Iced_coffee
