Ruggie’s favorite food is doughnuts, which is possibly from how his grandmother would make him doughnuts every year for his birthday in lieu of the birthday cake that they couldn’t afford.
Ruggie’s Disliked Food: Anything Rotten
Ruggie’s “Least Favorite Food” in his profile is listed as “anything rotten,” and he also has voice lines about being willing to eat anything, as long as it isn’t rotten.
Ruggie grew up with food scarcity back home (more here ▶︎ ) and it seems possible that his familiarity with the taste and dislike of rotten food might have come from a situation where it was all he had (not officially confirmed).
Ruggie: “Back in my hometown I was always looking for something to eat. Weeds and that sort of thing.”
Ruggie has a comment in Book 2 on EN of Azul’s potion tasting like “stew someone aged in gym sock,” adding a light-hearted twist to his actual dialogue of, “Tastes like rotten stew!,” and Ruggie’s “rotten stew” comment was also altered in the English-language translation of the novel (“old stew simmered in a gym sock”).
The comment was retained in the EN manga, so only EN-manga readers have this reference to Ruggie’s disliked food and, possibly, what was meant to be a hint at his childhood: does he compare the potion to rotten stew because that is a taste that he knows? From a time in his life when it was all he had?
All conjecture (as of this writing), but interesting to consider.
Twisted Wonderland Reference Note 