The use of common commercial trademarks in movies and TV seems very random. Sometimes a character is drinking a Coke, sometimes it's a "Dr. Cola" (fake). Sometimes a MacBook is clearly a MacBook, sometimes it's a MacBook with a sticker placed just so, to cover the emblem.
And as a subquestion, when movies/TV do use a real product, who is paying who? Is the soda company paying for that movie to feature their product, or is it the other way around? (The movie is paying to use that soda company's product) Or is no one paying at all, and there is a fair use exception for common products?