Mountains of mashed potatoes. Waterfalls of chocolate cascading over brownies. A steaming hot turkey leg. The sweet bite of a crisp Fall apple. Mmmm…I made sure not to write this when I was hungry.
The food in your story is important. No, really, it is. For any genre. Food combines the sense of taste, smell and sight and creates its own image for the reader to place the scene. By referencing a specific type of food, you can create a setting either in location, time or both. Meals, snacks or articles of food are surprisingly vital to the background description of your story and forming a solid picture for the reader.
For Contemporary: In order to help set your story in a location, research what people in that area eat. This will differ by country (Japan vs India) or even State within the USA (Maine vs Florida). Specific things your characters consume, like a Mellow Yellow, might give the story authenticity as a Southern narrative compared to your MC drinking a Sprite. And be sure not to have anyone chewing on something that has been discontinued decades before.
For Historical: Eating and drinking was a difference experience even twenty years ago. In my case, I was eating pureed pears and carrots. But this change should be integral to your description especially if your novel is set decades or centuries in the past. There might not be utensils. Or fast food chains. Or the microwave. Again, do your research and be sure the items your characters consume were actually available at the time of the story.
For Speculative: This category offers a bit of leeway as far as research goes. You should definitely gain knowledge regarding the type of food your story has, but because the plot is speculative by nature, the food can be too. Be creative, but be realistic too. In this case, take the time to skillfully describe how the meals are different to show how society has changed or is different from the one we know.
In every story I read, I notice the food. This might be because I’m a foodie at heart, but I think it’s more closely tied to the fact that food displays cultural differences that are straightforward facts yet subtly showcase the uniqueness of a setting. You don’t read a book for the food the characters eat. But you remember the pumpkin juice at Hogwarts. The colorful candy wrappers of the 20’s. The plum and lamb stew in Panem. People eating with their hands in ancient Greece. The gurgle of Anne Frank’s stomach. Food is important. Way more than you think.