What cup is in Hashem's hand?
Rashi: It is a cup of Tar'elah (bitterness or poison).
Radak: He will give to the Resha'im among the nations to drink when He gathers the exiles. Then He will lower the nations and raise Yisrael. Yisrael already drank from it in Galus - "Es Kuba'as Kos ha'Tar'elah Shasis Matzis" (Yeshayah 51:17).
Malbim: Straightness says also this. Hashem constantly influences good, Brachah and Chesed without ceasing for a moment. Sometimes a person receives evil. This is not from Hashem, rather, because he did not want to receive the good influence from Hashem. Rather, he receives the dregs. The verse depicts that Hashem has a cup of influence of choice wine. It is full, even though He constantly pours and influence from it. Resha'im get the dregs because they do not want to drink the good wine, i.e. they do not prepare their deeds to receive His Brachah.
What is "Yayin Chamar"?
Rashi: It is strong wine.
Radak: The wine is red. This is an attribute for wine - "Al Tere Yayin Ki Yis'adam" (Mishlei 23:31).
Malbim: It is choice wine.
What is the meaning of "Malei Mesech"?
Rashi: It is full and mixed 1 ; it is ready to give to the nations to drink. Radak - this is like "Maschah Yeinah" (Mishlei 9:2).
Wine used to be very strong; people normally mixed two [or three] measures of water for each measure of wine. (PF)
What is the meaning of "va'Yager mi'Zeh"?
Rashi: From this cup He will spread and shower on their drinking parties. This is like "k'Mayim Mugarim" (Michah 1:4).
Radak: The cup will be so full that the wine will spill over on both sides. It says Malei and va'Yager (masculine), even though normally "Kos" is feminine, e.g. "Shemareha" (its dregs).
