Why does the Minchah of a Sotah comprise coarse barley flour, unlike all Menachos that comprised fine wheat flour?
Rashi and Targum Yonasan: Since she behaved like an animal, her Korban consists of animal food.
Ramban #1: Refer to 5:15:2:2.
Ramban #2, Moshav Zekeinim: Barley - 'Se'orah' - is symbolical of a storm-wind - 'Ru'ach Se'arah', which describes the horrific ending that followed the bringing of the Minchah 1 (in the event that the Sotah is guilty). And by the same token the earthenware vessel in which she drinks the Mei Sotah is a sign that she will be broken like an earthenware vessel, and the earth that is placed inside it, that she is about to return to the earth from which she was formed. 2
Rosh (12): She fed the Bo'el dainties, so her Korban is animal food.
Why was no oil or Levonah (frankincense) added to the Korban?
Rashi: Her Korban is brought unadorned - without oil, since oil is called 'light', 1 whereas she acted in darkness; and without Levonah, since the Imahos are called 'Levonah', 2 and she departed from their ways.
Ramban, Da'as Zekeinim, Hadar Zekeinim: The Sotah's Minchah is inferior, in that it is of barley and has no oil and frankincense because it comes to bring on her a punishment, 3 as opposed to other Menachos, which come to create goodwill between Hashem and the owner.
Why is Minchas Kena'os written in the plural?
Rashi (citing the Sifra): Because she has aroused the jealousy of two 'masters', Hashem 1 and her husband.
Why does the husband bring the Minchah on behalf of the Sotah and not the Sotah herself?
Ramban: Because it would be insensitive to ask the Sotah to pay for and to bring a Korban that will bring about her own death.
Why is the Minchas Sotah not listed together with the other Menachos in Vayikra?
Ramban #1 (on Pasuk 6): Because it is a Minchas Kena'os, and does not come to atone like the other Menachos.
Ramban #2 (6): Because it is part of the Parshah of Sotah, which the Torah presents here, in order to preserve the sanctity of the camp after having described its detailed Yichus, by determining the Mamzerim 1 via the law of Sotah.
Ramban: Who are not the children of their mother's husbands - following the latter's suspicion of their wives.
Who pays for the Minchas Kena'os?