okay so I know I’m probably not gonna find an answer but I thought I’d give it a try. I can’t remember the character or where the character is from. I don’t remember if it was a anime, manga, or novel but it was definitely one of those. The character put cinnamon in their hot chocolate. Now this had to do with their character because the MC would feel comforted when ever they drank the hot chocolate. The MC didn’t know the “secret ingredient” until something tragic happened to this character. Okay I think that’s all I remember. Have at it! I wasn’t sure where to put this and opted out for the novel section. Good luck and thank you if you know of it.
https://mangadex.org/title/2180/shinrei-tantei-yakumo-akai-hitomi-wa-shitteiru Here you go. Find those in 'Message from The Dead' chapter.