After the morning prayer, the Shulhan Aruch (Orah Haim 155:2) writes that it is highly advisable to eat a bread-based breakfast meal, known as PatShaharit. This is based on the Tur’s analysis (O.H 155) of the Gemara (Horayot , which says that a proper breakfast, consisting of bread, salt and water, can help prevent eighty three ailments which arise from the gall bladder. Rabbi Yosef Teomim (Pri Megadim 155:3) writes that one can fulfil the recommendation of a breakfast meal with any grain-based product (ie. Mezonot).
Rabbi Avraham Buchach (Eshel Avraham) says that one fulfils PatShaharitwith coffee. Interestingly, Rabbi Shabtai Lifshitz (Segulot Israel) explains that coffee is being beneficial for one’s memory. Additionally, the Kaf HaHaim (O.H. 157:29) says that wheat bread eaten with a soft-boiled egg and olive oil is useful for memory.
Rabbi Shmuel Wosner (Shevet HaLevi, vol. 4, § 16) clarifies that, although it is not a sin to skip breakfast, it is highly recommended to have it.
Summary: One should make a habit of eating a bread or grain-based breakfast.