In Montevideo we were able to find a brand without azúcar at the TaTa (a South American retail chain), but it was only one brand of ten or twelve offerings. Other stores only offered café con azúcar (coffee with sugar).
In Ushuaia and El Calafete the stores only offered coffee with sugar. We asked a tour guide in Ushuaia where we might find coffee without sugar and he said it might be available in Buenos Aires. Our tour guide in El Calafate put us on to a specialty coffee shop where William bought a small package of Colombian beans that they ground for him. Unfortunately it was flavored.
Upon arriving in Bariloche we were not surprised that the main supermarket only offered café con azúcar. We started the quest for coffee without sugar, stopping in every small grocery store or specialty store we came across. Often we received puzzled looks - why would anyone WANT their coffee without sugar? Most people add more sugar. I suppose their puzzlement makes even more sense when you consider that Bariloche is the chocolates capital of Argentina and also home to the Havana brand alfajores plant. Several days into our stay we stopped into a store near an area filled with hostels. There on the top shelf we found a few of bags of Café Cabrales brand labeled "libre de azúcar" (free of sugar). We bought a couple of bags - enough for Bariloche and a start on Mendoza.
Mendoza is a larger city and we had hopes, but they were dashed with our first visit to the supermarket where we only found café con azúcar. However Mendoza is also a larger city and with that comes the prospect of more international brands. As much as William despises the Starbucks we find seemingly every few blocks in cities around the world, he was now hoping for a Starbucks in Mendoza.
Google maps reveals four Starbucks, two within one mile of our apartment. As we walk through the door of the closest store William focuses immediately on the packaged coffee looking for a dark roast. After confirming it is sin azúcar he asks to have it ground for a french press. Ten minutes later and the equivalent of $10 lighter William walks out of the Starbucks with a smile on is face.
Sometimes a situation causes a change of heart, at least on a temporary basis.