How medieval is this? Nuts and dried fruit may be an option. It's easier to carry lighter food. Hard tack is just water and flour cooked, no leavening, maybe salt added. Water is more of an issue with walking than eating.
Will they hunt and fish? Fishing can be more successful than hunting. Fish can be smoked and dried if they have the time or just cooked it will keep for a few days.
The setting is reminiscent of very early middle ages, particularly Antiquity/Medieval Ireland. However, I don't see water as an issue as one of the MC's is skilled is ice based magic. He is able to freeze the vapors in the air into a liquid state.
As for hunting, aside from the ice magic, the other carries a sling, so they can hunt using slings/magic.