Hello! This question was answered eight months ago here. /u/Eyestache answered it pretty succinctly:

Dried fish (harðfiskr), bread, meat preserved in whey, and whey itself would have been commonly eaten aboard ships, if there were no islands near enough to stop at. That said, though, in most of the sagas where there is a long duration of shipboard travel, we don't get any descriptions of the food that is eaten.

/u/vonadler gave a broader scope of Scandinavian peoples:

Early medieval Scandinavian people probably ate more protein and fat than most continental people. Dairy, wild fowl eggs, fish, blubber (from whales and seals), meat (mostly pork, but whale and seal too) peas and beans were common parts of their diet, while the staple bread was coarser and often mixed with bark. In fact, grain was probably more often brewed into weak, dark and cloudy beer (1-2% ABV) or boiled into porridge than baked as bread.

You might also be interested in reading up on pemmican, a mixture of dried meat that has been pounded into a powdery consistency and mixed in a 1:1 ratio with melted fat. Sometimes dried berries were pounded up and also mixed into the mix, which was then placed into a rawhide bag for storage. It was eaten raw, in a stew, or pan-fried. It was invented by American Indians and mostly made of meat and fat of large game like bison and elk, though it can be made of the meat and fat of any animal.