Should one eat Mezonos and say the blessing of Leisheiv Basukkah after shaking Lulav?
Some Chassidim are particular, based on an acclaimed oral statement of the Rebbe to a certain individual Chassid during the Yom Tov meals, to eat a Kibeitza of Mezonos and say Leisheiv Basukkah after shaking the Daled Minim, as perhaps the shaking itself requires a blessing. Some Rabbanim have testified to the accuracy of the claim, while others state that it is the novelty of that particular Chassid based on a talk of the Rebbe and was never explicitly said by the Rebbe and hence its claim is baseless. Practically, all agree, even those who testify for its accuracy agree, that such statements said to an individual during a meal does not pass the bar to become an established Chabad custom, especially based on the fact that the exact wording and contents of the Rebbe’s is not known. Furthermore, it does not seem to have any real Halachic necessity, and therefore there is no need to be particular in following it, although those who want to may do so, so long as doing so does not transgress the prohibition against eating prior to prayer which is only permitted to be done if one is sick or needs to do so for extra concentration.
 See Koveitz Pardeis Chabad Vol. 14 [Oberlander]; Hearos Ubiurim 879 [Kloizner], 887 p. 59 [Korf], 951 [Oberlander], 970 [Teichman], 971 [Shapiro]
 There is no documented source for this statement from the Rebbe, and it is based on an acclaimed oral tradition from a statement the Rebbe made to an individual during one of the meals.
 This custom is recorded in all the following Sefarim as a custom that should be followed: Otzer Minhagei Chabad p. 294; Shaareiy Halacha Uminha Vol. 5 p. 133; Siddur Raskin p. 470 footnote 9; Hiskashrus Gilyon 426 p. 13; 481 p. 15
 Rav Label Shapiro in Hearos Ubiurim 971 that so he remembers hearing from the Chassid Rav Dubriskin that so was answer to him by the Rebbe during the meal, that according to the Sicha that he said that day one should eat Mezonos after shaking Lulav.
 Koveitz Pardeis Chabad Vol. 14 [Oberlander]; Hearos Ubiurim 879 [Kloizner], 887 p. 59 [Korf], 951 [Oberlander], 970 [Teichman] who spoke to the son of Rav Mondshine who agreed that it was a mistake to enter it into Otzer Minhagei Chabad as it is a baseless rumor
In addition to the fact that we do not accept unsubstantiated rumors in the making of halachic decisions [See Igros Kodesh 8:332; 20:82; Maaneh of Rebbe in Introduction to Sefer “Likkut Piskeiy Halacha Uminhag”; Mikdash Melech 1:61; Tzemach Tzedek E.H. 413[ the above authors explain that in truth the source for the above rumor is from a Chassid named Rav Dubriskin, who deduced this from a talk of the Rebbe, and is not from the Rebbe himself. His own son, who in a counter article brought a story with a different Chassid and the Rebbe to prove the rumor, in a follow-up article debunked that as well as being incorrect after the person he quoted, called him up and told him that what he wrote in his name is not accurate. Thus, we see of the very unprofessional and risky path of making Halachic decisions on unsubstantiated claims.
 Rav Label Shapiro in Hearos Ubiurim 971
 As a) the shaking of the Lulav in the Sukkah is only a Mitzvah Min Hamuvchar, and is thus similar to drinking water in a Sukkah, which does not require a blessing of Leishev Basukkah to be recited. B) In any event, the blessing of Leishev basukkah that is recited anytime during the day exempts all the actions of that day, and there is thus no reason to require it specifically after shaking Lulav.