Yiddish: It's as helpful as an afikoman for a fever.

It's no help at all.   SOURCE: Stutchkoff, Der Oytser fun der Yidisher Shprakh.  The afikoman is a piece of matzo which is set aside during the Passover Seder to be eaten after the end of the meal. Kadokhes is a malarial fever, or high fever with shaking chills, once commonly known in English as ague.  See also:

afikoman in a riddle     kadokhes in a curse

עס העלפֿט ווי אַן אַפֿיקומן צו קדחת.

Es helft vi an afikoymen tsu kadokhes.

It's as helpful as an afikoman for a fever.