Your character can drink a Coke, drive a Ford F-150, and shop at Target. When you use trademarks in a descriptive sense, you are not violating the trademark holder's rights. You are merely describing what the character is drinking or driving and where the character shops.
IF, however, the Coke, the Ford or Target figure prominently into the plot of your novel (the character is poisoned by Coke, the Ford blows up, Target won't honor a sales price and chaos ensues), or if the title of your novel capitalizes off the trademarked name (A Coke for Cathy, A Ford in Frank's Future, Terror at Target), then you run into problems, as you would if your advertising or cover uses the trademarked names to sell the books. You should be careful not to disparage the product or service that you name.
Fair use is determined at the court level so, unless or until you are sued by a copyright or trademark owner, you have no way of knowing for sure if your use of copyrighted material or a trademark is fair or not. It is ALWAYS wise to have your novel reviewed by an attorney prior to print, to eliminate wherever possible any potential lawsuit magnets, and it is also wise to have your novel insured in case a lawsuit arises from its content, despite your best efforts to avoid one.
