Yosef Karo

“ The custom among all the Diaspora of Ashkenaz is to eat a proper meal before Mincha, and afterwards to recite Mincha and then eat a "Seudat Ha-mafseket" (Maharil) . The custom has become to make the first meal a little larger, in order that the fast not harm them so much, since we are stopping [eating] while it is still day like on "Yom Kippurim", and there is a little bit of a proof for this in Midrash Eichah Rabati. ”

“ Even for other drinks one should reduce their consumption from what one is used to drinking (Tur with Beit Yosef in the name of Tosefot and Rokach) , similarly one should not eat radishes or salty foods after their meal, things which one is used to do on other occasions, in order to act with abstinence. ”

“ Shulchan Aruch Orach Chaim 552 Laws of the day preceeding Tisha B'Av
דיני ערב תשעה באב
552:1 On the day preceeding Tisha be-Av, a person should not eat meat as part of their Se-u-dat Ha-maf-se-ket {lit. Finishing Meal - the last meal before fasting}, which is eaten after midday, and one should not drink wine and one should not eat two [different] cooked dishes. ”