Q. Dear Rabbi, I know that on Rosh Hashono we are not supposed to eat bitter or sour foods and drinks. If these are sweet too, such as most common soft drinks, or salad dressing that has a bit of vinegar to make it tasty, or sweetened prepared chrein, Is there a problem? Thanks.
　
A. The Minhag not to eat bitter or sour foods as a Siman or symbol for a sweet new year, goes back to the time of the Geonim. (Tshuvos Hageonim 114 – Chida in Tov Ain 18: 91). Mishna Berura (583: 5) mentions only not to eat foods cooked with vinegar. Chida (More Baetzvah 9: 254) includes lemons too.

Many Poiskim differentiate between things sour or bitter (vinegar, chrein) and sharp tasting foods (pepper, onions, charif or jalapenos), permitting the latter as they are mainly condiments and make the food taste better (Bikurey Chaim 2: ,3, quoting R.N. Gestetner Shlit’a – Kovetz Minhogei Isroel 5, p.135).

Rav Yisroel Dovid Harpenes in Mikdash Israel (Yomim Noroim 111) permits sweet lemon tasting soft drinks or tea with lemon and sugar, as they convey the positive idea of a sour or acid taste being changed into sweet, similar to the salt in the chala being transformed by dipping it into honey. By the same token, he sanctions eating salads with dressing that has a bit of vinegar; he also permits grapefruit with sugar and prepared sweetened chrein (ibid. 110, 112, and 113). He quotes Horav M. Feinstein ZT”L as saying (on eating fish with chrein) that its good taste symbolizes a “geshmak’n yohr”, a good tasting year.

Horav Shlomo Miller’s Shlit”a opinion is similar, however he disagrees about chrein and recommends not to eat it, as its bitter taste dominates, and it is also used as Moror or bitter herbs on Seider night.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a.