The Ben Ish Hai (Rav Yosef Haim of Baghdad, 1833-1909), in Parashat Vayelech, records a custom to dip one’s bread in honey or sugar during the "Se’uda Mafseket," the final meal eaten before Yom Kippur. Hacham Ovadia Yosef notes, however, that even those who follow this custom must ensure to have salt on the table, as well, and to dip the bread three times in the salt, as is always done, even if one also dips the bread in honey or sugar.
There is a Torah obligation of "Tosefet Yom Ha’kipurim," or adding a few minutes onto the observance of Yom Kippur. The Torah writes that the Yom Kippur observance begins "Be’tish’a La’hodesh Ba’ereb" – "on the ninth of the month, in the evening" (Vayikra 23:32), indicating that the fast should begin on the ninth of Tishri, the day before Yom Kippur. Therefore, one must begin his observance of Yom Kippur a few minutes before sundown on Ereb Yom Kippur. This applies not only to fasting, but also to the other prohibitions observed on Yom Kippur – bathing, wearing leather shoes, and so on. Hacham Ovadia Yosef writes that there is no specific period of time that one must add onto Yom Kippur, so one fulfills this obligation even he begins the observances of Yom Kippur just five minutes or so before sundown.
One who finishes his "Se’uda Mafseket" and then wishes to eat or drink may do so, provided, of course, that the time to begin the fast has not yet arrived. This applies even if he recited Birkat Ha’mazon. So long as the time for the fast has not arrived, one may continue eating and drinking despite the fact that he completed the formal meal.
There are currently on the market a number of pills and suppositories that one can take to help alleviate the discomfort of fasting, such as capsules with timed release that send different kinds of medication throughout the body over the course of the fast. Hacham Ovadia maintains that a healthy person should not take such pills or suppositories, as this would constitute "Nabal Be’rshut Ha’Torah" (violating the spirit of the law, even though it is technically permissible). Once the Torah commanded us to "afflict our souls" on Yom Kippur, it is wholly inappropriate to look for ways to fast without discomfort. Hacham Ovadia does allow taking these medications in cases of a weak or ill person who might otherwise be forced to break his fast on Yom Kippur, or might faint. Barring these exceptional circumstances, however, a person should not make use of these medicines to help alleviate the discomfort of fasting.
Summary: It is customary to dip one’s bread in honey or sugar during the final meal before Yom Kippur. One must ensure to begin all the Yom Kippur observances at least several minutes before sundown on Ereb Yom Kippur. It is permissible to eat and drink until that point, even if one completed his meal. One should not take pills or suppositories that alleviate the discomfort of fasting, unless he would otherwise become so faint that he would have to break his fast.