The hangover cure Santiago gives Peralta (that he drinks) is a combo of liquid gelatin and peaches cut to look like egg yolks.
Jimmy Brogan's character was evidently based on Pulitzer Prize winning author Jimmy Breslin, an American journalist and author. Breslin was well known for his columns in various New York City newspapers as well as several novels.
When Captain Holt corrects an inaccurate statement made by Peralta, Peralta responds by saying "eh, six of one." This is short for the colloquialism, "six of one, half-dozen of the other," another way of saying "potato, po-tah-to." In other words: "we're both saying the same thing." Of course, Jake's original statement was not at all true, so his qualifying remark is more whimsical denial than anything.