Grim doesn’t seem to have a particular preference for one type of food over any others, equally excited about fruits, vegetables and meat, saying, “I’d eat fruit every day if I could afford ‘em on our lousy budget.”
We also see Grim excited about ice cream, bread, coconut milk, lemonade, apples, sandwiches, eggs, tarts, chicken, doughnuts, pudding, churros, and grass.
But he may enjoy tuna more than anything, accepting a can of tuna in exchange for performing a dangerous task for Azul, asking for tuna as payment for photos during Halloween and having the prefect promise him tuna in exchange for his cooperation in the Prologue.
Grim says that if he had magic like Trey’s he would be eating canned tuna for every meal and often refers to the VDC as his opportunity for a “tuna bonanza” during Book 5.
During the Playfulland event Lilia struggles to keep Grim from leaping out during a ride to eat tuna fish, and Grim successfully bites one in another attraction.
Leona has him physically restrained and carried away by Jack, Kalim and the prefect to keep him from eating the fish.
Grim is a member of the Gastronomy Club, and he says that “eating stuff like looks edible is a legitimate Gastronomy Club activity.”
We get more detail in the novel, where we learn that Grim founded the Gastronomy Club himself after all he wanted to do was eat and all the clubs tangentially related to food refused his application. Grim is often complaining about being hungry, as seen in Firelit Sky, Harveston, Vargas Camp and Book 1 through 6.
Multiple characters comment on how much Grim eats, with Jade, Deuce, Riddle and Idia all commenting on how he has a one-track mind when it comes to food.
While Grim will eat at every opportunity he can become full, eating too much during Firelit Sky and Book 4.
Twisted Wonderland Reference Note 