Is there a Minhag not to eat Pickled meat on Rosh Hashanah thru Shmeini Atzeres? And does it make a difference if the food does not taste pickled e.g cooked in a sweet sauce?
The minhag is not to eat sour foods on Rosh Hashana etc., if the food is spicy, there are numerous poskim that say that it is not an issue. Additionally, if the food has a sweet taste and not specifically a sour one, even though it has vinegar or lemon juice in it, it is permitted. It is for this reason that it is permitted to eat ketchup, even if it contains vinegar, because it has a sweet taste. The same would apply to making a dish that is sweet and sour, or placing lemon into tea- it is permitted since the tea does not have a sour taste.
Have kesiva v’chasima tova
Mateh Efrayim 583-3, M:B 583-5, Ashrei Hoish O:CH 3-chap. 14-6, Kovetz Halachos (Yomim Noraim) 7-21, Piskei Teshuvos 583 ftnt. 30, Mekadesh Yisroel 111, Poskim.