My headcanons for the Primarchs’ notable favorite foods and drinks:
Curze: Slightly stale pastries that he used to rightfully redistribute into his stomach (steal) from bakeries disposing of them when he was a kid. He doesn't like fresh food at all but eats anything. If he finds a complicated pastry he'll 'autopsy' it by seperating the icing and crust and jams and eats it all slowly.
Sanguinius: human meat that has been detached very recently, but seeing as this is unethical he also accepts live insects or seafood as this doesn't make other people think he's insane.
Fulgrim: the paste/slop they feed servitors. He's used to it from consuming it in the mines, and it always has a distinctive chemical aftertaste that's appealing to him. He eats it in secret and acts like he prefers the finer revelry in front of others.
Angron: likes getting horrifically inebriated, only drinks alcohol that's 'fresh' because he thinks being offered expensive old alcohol was some sort of insult to his background.
Mortarion: has low sense of taste, and doesn't like eating or drinking anything particularly. Likes seeing other people eat and the parallel socialising aspect of eating so will accept eating distantly with someone while discussing things. Hates wasting food, will eat rotten or spoiled things because of this.
Magnus: missed his developmental milestones and finds eating and digesting gross on a sensory level. didn't manifest a digestive system until he was instructed to as an adolescent and didn't like it. Will chew and spit things out occasionally if someone's insistent on eating with him. will eat those candies that have toys inside of them.
Russ: Has no particular preference and likes everything, excluding when anyone else is eating near him in which case he wants what they have to an extreme ravenous level. Russ, Freki and Geri have to be fed in different rooms or it's a disaster
Dorn: a traditional inwit desert you eat on your birthday. He refuses to eat it on any other day and doesn't want an adapted size that would actually satisfy him. Roughly he feels it reminds him of his late dad because he decided what day would be celebrated for him and did it religiously.