Bear with me here, I swear I will get to the food stuff, but first a bit of background.

The sources we have for these voyages (a collection of sagas and two other works known as "The Book of the Icelanders" and "The Book of Settlement") are all at least 2-4 centuries later than the supposed dates of exploration. This is a fairly typical problem in Scandinavian history. These are oral tales handed down for several generations and then written. The info in them is thus problematic. All that being said, archaeological evidence and our understanding that just because something is "fantastic" doesn't make it "fantastical" all point to a Scandinavian presence at the very northernmost areas of Canada.

North Atlantic travel and exploration consists of four major locations: Iceland, Greenland, Helluland (likely the island of Baffin in far northern Canada) and Vinland (modern Newfoundland).

Travelers to North America would have been coming from Iceland (the major North Atlantic settlement area) and Greenland (much less well settled and abandoned by the 14th century).

And now on to the food. Fish, fish, and fish would have been a primary food source. Some fresh, much of it salted and preserved. Blubber and whale meat are a possibility as well (though they probably would not have actively whaled during their voyages). Meat (seal and caribou especially if coming from Greenland), salted or even fresh. Also sea-birds. For a particularly amusing glimpse of what things might have looked like, check out this (admittedly very blurry) video of a reenactment of a voyage from Ireland to America, in which a fellow is picked up solely for his ability to catch birds and fish.

They would also have had livestock, pigs, sheep, and perhaps even cattle, that could be fresh slaughtered but would ideally have been kept for secondary production (cheese, milk, wool etc.). We know from archaeological remains and from patterns of settlement westward that these voyages would have included both men and women and thus probably were supplied with the necessary goods (including farm animals) to at least begin settlement. This means that they might also have had cereal for planting and cultivation.

It is best to think of the voyagers to America and the North Atlantic as rather distinct from the "Vikings" most famous for raiding England, Ireland and Francia in the 9th century. These are not bands of warriors looking to make money and head back home to Norway, Denmark, and Sweden. They are explorers and above all settlers, looking for new lands and new opportunities.

Sources: The first and best place to go is The absurdly large edited volume, The Viking World which has several articles on North Atlantic settlement and travel, all of which have bibliographies.

Happy reading!