In the film, Back to the Future, when Marty gets stuck in the past (1955), he goes to a known dinner from his time and asks for the address of Doc Brown, to which the server angrily asks him to order something, in response to which Marty asks for a “Pepsi Free, ” and the server replies, “If you wanna Pepsi, you’re gonna pay for it”.
So, one thing that perplexed many viewers is why and how Pepsi Free was in Marty’s own time, how he knew about it and was Pepsi Free during that time (in 1985) in the real-life USA.
Why Was Pepsi Free in 1985?
Pepsi Free was a caffeine-free version of Pepsi introduced by PepsiCo in 1982. It is why Pepsi Free would have been familiar to Marty in 1985, in his time.
However, when Marty went back into the past (in 1955) and asked for a Pepsi Free, the server assumed he was asking for a free Pepsi because the server was unaware of Pepsi Free in 1955.
So, it was a joke about the drink Pepsi Free, which sounds like Pepsi is free, to the server in 1955, and a reference to PepsiCo, which became the first major brand to sell caffeine-free cola in 1982.
Marty also asked for a Tab, a diet cola introduced by the Coca-Cola company. The joke in the movie is that neither drink (Tab and Pepsi Free) existed in 1955.
In 1987, two years after the movie was released, Pepsi phased out the term “Pepsi Free” and renamed it “Caffeine-Free Pepsi,” and it is still known as Caffeine-Free Pepsi.
Another hint that Marty was aware of Pepsi Free is that in one of the scenes, a can of diet Pepsi free can be seen next to Marty’s clock radio in his present time, in 1985.