I do not know the answer to this, even though it comes up every Shabbos.
My usual behavior is not to make a bracha on the glass of juice between fish and meat. I don't know if this is correct.
I certainly wouldn't know if it were correct if it were, say, a piece of bread between dairy and meat. (Would one make a blessing on this bread? Which blessing? I assume one would wash. Would one bentch? [Notably, the standard advice--"eat some bread and wash on everything"--doesn't work.])
Various considerations; please feel free to skip reading them: 1. The idea that we make a new bracha on a l'chaim during the meal. (But it seems this is quite complicated, and may only apply to wine, and then only in some cases, possibly depending on the machshava during kiddush, and on whether one drank kiddush immediately.) 2. More generally, the idea that we make a new bracha on anything (i.e., dessert) not considered part of the meal -- although this too seems to be really complicated. 3. The idea that we don't make a bracha on liquids. 4. The idea that we make a bracha on some liquids. 5. The idea that the palate-cleanser is tafel to the meal. Even bread as a tafel (i.e., with salty fish) doesn't get a bracha. But does that apply here? And what if there's no [single] meal? 6. The idea that we might have nutritional, taste or other benefit from the palate-cleanser, even if its primary purpose is to fulfill a halacha. (And even then--I've never heard of not making a bracha on something consumed to fulfill a halacha.) 7. Wine/alcohol and bread, in particular, are sometimes deemed "important enough to get a bracha" in various situations. So if one were being used as a palate cleanser, maybe it would get a bracha. 8. In deference to these authorities, maybe the best course to say shehakol on something else before the meal and drink less than a revi'is total to cleanse the palate. But how much is necessary to cleanse the palate? And what if the palate-cleanser is bread? 9. Safek berachos lehakel. But I don't know about safek safeika berachos lehakel, which seems to apply to brachas on food,drink. (It would seem that in such a case, you could or even should make the bracha. {Or maybe not.}) But is a palate-cleanser "food"? 11. Would having the palate cleanser in mind at the moment of kiddush and/or hamotzi definitely mean you wouldn't need a bracha later? And which one should it be -- kiddush or hamotzi? Does it depend on what you will use to clean your palate? 12. Would @Cashcow 's suggestion here work -- to eat a bit of bread with your drink (and/or with your kinuach bread) thereby making it part of the meal? 13. It seems that the Mishnah Berurah rules that palate-cleansers need a bracha. (But there is still the question of whether it is covered by Hamotzi/kiddush in the case of palate-cleansers consumed during a meal.) 14. Vezot HaBracha (p. 72, chapter 8) rules that on fruit juice one doesn’t make a Bracha during the meal. (Also saw here that one doesn't on water, but that doesn't help much.) Sorry if it seems to be a lot of questions in one...I have no idea how to divide it
