The Sages ordained that before fulfilling the mitzva of dwelling in the sukka, one recites the berakha of Leishev Ba-sukka: “Blessed are You, Lord, King of the Universe, Who has sanctified us with His commandments and commanded us to dwell in the sukka.” There are different customs as to when one recites this berakha.
According to many Rishonim, including Rif and Rambam, whenever one enters the sukka to spend time there, even if he intends only to sit without doing anything, he recites Leishev before sitting down, since he is fulfilling a mitzva. This is the practice of Yemenites; they recite the berakha while standing, immediately upon entering the sukka, and then sit.
All other communities follow Rabbeinu Tam’s view, namely, that the berakha is recited on eating, as it is more central. The berakha on eating then covers everything else that one does in fulfillment of the mitzva of sukka. Even though sleeping is also important, we do not make a berakha over it, since one might recite the berakha before going to sleep, and then not fall asleep. Eating, however, is in one’s control, so it is proper to recite the berakha over it. The question is: What type of eating mandates a berakha?
According to Ashkenazic custom, one who plans to eat an amount of food that makes eating in the sukka obligatory makes a Leishev. One who does not plan to eat that much while he is in the sukka should still make a Leishev even if tasting a minimal amount of food or wine. If one has no intention to eat at all, many have the custom not to recite the berakha, but some have the custom to recite the berakha even when just spending time in the sukka; this is the proper practice.
According to Sephardic custom, one recites Leishev on a significant amount of food that generally constitutes a proper meal. In this respect, there is a difference between bread and other types of mezonot. For bread, even when one will eat only a bit more than a keveitza, he recites Leishev. On other mezonot, be it baked goods, pasta, or porridge, only if one eats an amount that will satiate him at a regular meal – approximately the volume of 4 eggs – recites a Leishev.
It would seem that nowadays, even according to Sephardic custom, one must recite the berakha if they are eating a full meal (such as soup, meat, rice, and potatoes), even if it does not include bread or mezonot. Even though in the past the ruling was not to recite Leishev on a meal without bread, nowadays, when many people eat an entire significant meal without grain, it is also considered a se’udat keva, and one must recite the berakha. Nevertheless, one who knows that his parents do not recite Leishev on this type of meal may follow their practice. In order to remove any doubt, however, it is preferable that he take care to eat bread with such meals and recite the berakha.
According to Taz, Ḥayei Adam, MB 639:48, and Ḥazon Ish, the practice of reciting Leishev before eating applies when one plans to eat. However, if one enters a sukka and knows that he will not eat, no matter how long he stays in the sukka, should recite the berakha anyway, on spending time in the sukka. According to Ma’amar Mordekhai (8), one recites the berakha only when eating something that must be eaten in the sukka. Many Ashkenazim recite Leishev if they have any amount of mezonot, wine, or another significant food, as the primary position follows the view that the berakha is recited on spending time in the sukka, but since the custom is to recite the berakha when eating, they eat something and thus recite both berakhot. See Harḥavot 5:9-10.
. See n. 5 above, where we explain that one who makes a se’udat keva of meat or cheese and side dishes must eat in a sukka. However, R. Ovadia Yosef writes that he should not recite the berakha (Yeḥaveh Da’at 1:65), as Sephardim recite the berakha only over a meal containing enough bread or mezonot to be considered a se’udat keva (Sho’el Ve-nishal 3:95 and 165; Ḥazon Ovadia, p. 136). Ben Ish Ḥai limits the recitation of Leishev to meals with bread. However, it seems to me that their views apply to previous generations, when every se’udat keva had bread, or at least mezonot. Nowadays, though, when many people have se’udot keva based on other foods, these are considered significant meals, and Leishev should be recited. To this we can add the view of most Rishonim that one recites Leishev whenever one sits in the sukka, as well as the view of those (cited in the previous note) who maintain that if one does not intend to eat, he should recite a berakha on spending time in the sukka. This is also the ruling of Responsa Devar Ḥevron OḤ 586.