Question

May I suck on Zyn nicotine pouches on a fast day, and in general do they require a blessing upon placing them in one’s mouth? Many of them come with a flavorful taste, and one ends up swallowing that taste in saliva, similar to gum.

Answer

Based on the fact that these pouches have flavor and that the taste is swallowed with saliva, a blessing of “Shehakol” should be recited prior to placing them in the mouth, similar to gum.
At the same time, it is prohibited to place these pouches in one’s mouth on a fast day, since they have a flavor that is swallowed and are considered like food. This is in line with the rule that even tasting food on a fast day established by the Sages, such as the Fast of the 10th of Tevet, is forbidden.

Sources:

See regarding the recital of the blessing of Shehakol over gum: Beir Moshe 2:12; Kinyan Torah 5:17; Yabia Omer 7:33; Piskeiy Teshuvos 202:34; See Chayeh Adam 49:4

See regarding the prohibition of even tasting food on a fast day: Rama 567:1; Admur 612:7; Rama 567:1; Tosafus; Hagahos Maimanis; Terumas Hadeshen 158; Levush 567; Kaf Hachaim 567:10; Piskeiy Teshuvos 567:1-2