Q. Is there a shiur or amount of food that one should eat in order to comply with the mitzva of eating on Erev Yom Kippur? If not, should one keep on eating small amounts during the day or suck a candy to extend the compliance on this mitzva? Is drinking included?

A. Minchas Chinuch (313: 16) maintains that one complies with this mitzva only if he eats the amount of a koseves hagassa (A type of date, slightly less than a beitza or egg, Shulchan Aruch 612:1, or about 44 ml.) which is the prohibitive shiur of eating on Yom Kippur.
However, some Poskim write that the minhag is to eat also small amounts often, since one also complies eating small amounts (Ksav Sofer 114, Piskei Teshuvos 604: 2).
Drinking is also included (Mogen Avrohom and others, Mishna Berura 604: 1). I
Horav Shlomo Miller’s Shlit’a opinion is similar in regards to the shiurim, but the Rov disagrees with the minhag some have of eating small amounts of food throughout the day.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a