What looks like food, tastes like food, smells like food, sounds like food when you cook it, is grown in dirt like food, fills up your stomach like food, but is not food?
A poisonous mushroom. Since some types of mushrooms are edible, it can be very hard to distinguish between a safe mushroom and one that will kill you. Food is defined as a substance consumed to provide nutrition, therefore a poisonous mushroom that kills you doesn’t qualify as food, even though it shares all of the traits of a regular mushroom.
Other valid answers include anything that’s edible, resembles food, but is poisonous.