Ai isn't that bad, you just have to hand constant combos going which can be determined by rng with the board but is controlled by the player. You can also try turning down the difficulty in the settings. I think for the maximum food challenge, I used a character with high cold resist and then chose all the cold foods during the single player cold challenge and got the unlock.
My final note, I don't know how much the difficulty setting affects the game, but if you keep your combos going you can dominate. I play on the very hard difficulty because I would be stomping on the CPUs