Editors are frequently asked whether it’s permissible for writers to mention product or business names in books. The short answer is yes.
The long answer is be careful.
By the nature of doing business, companies put their brands into the public forum and in fact usually appreciate publicity. But you do need to ensure you’re not needlessly casting them in a negative role.
For example, if your novel takes place in Ybor City, Florida, it would create a great sense of place to have your characters dine at the historic Columbia Restaurant, founded in 1905. That would cause locals to say, “yeah, I know that restaurant.” It adds realism to the story.
Maybe you don’t need to specify the town, but you want to mention Denny’s because you need a place where your characters can meet in the middle of the night. That’s fine. But if it will be a crime scene, it’s probably better to make up a fake all-night diner.
Trademark owners can’t stop you from using their product names: your hero can drive a Toyota to Starbucks and work on his MacBook. The trademark owner will ask you to capitalize it as registered, as the capital B in MacBook, and they would prefer that you not use it in a negative context, e.g., “the victim was found in a Dumpster behind Denny’s.” (Note Dumpster is capped because it’s a trademark!)
Trademark owners often ask that their trademarks not be used in a way that doesn’t represent their product. An editor at the newspaper I used to work for once used the phrase “snap crackle pop” in an editorial that had nothing to do with breakfast cereal. She got a cease-and-desist letter from Kellogg Co.’s trademark lawyers. But if she had used the phrase to describe Rice Krispies, we’d have been fine.
Libel is another matter. One must be careful not to defame a person, product, or company in writing, unjustly. Those writing about the financial crisis need pull no punches in naming the companies that contributed to the housing market boom and bust, as long as what they report is true. But if, for example, your memoir speculates about malfeasance at a company but you lack proof, you’d better run the story by a lawyer first. News organizations do this often.
You don’t need permission to refer to a company or product by name. But do ensure that you are doing so in a respectful way.