What are "Shefos Bakar"?
Rashi citing Targum Yonasan: They are cheeses of cows' milk. Radak - they are called Shefos because they are made (curdled) with "v'Shufu Atzmosav" (Iyov 33:21; ground bones 1 ).
I did not see anyone else mention using ground bones to curdle, until about 700 years after Radak; Divrei Yosef (6) says that recently, chemists found a way to do so. (PF)
How did they know that they are hungry?
Rashi: They did not take enough provisions, for they left hastily and fled.
What is the meaning of "v'Ayef"?
Radak: They are tired from traveling, like it says above (16:14 - "Ayefim v'Yinafash").
Radak citing Yuma 77a: It is weary from killing.
Why were they thirsty?
Radak: Even though they were among settled places, where animals graze, much water is not found.
