When Marty McFly leaves Doc Brown’s garage because he is late for school, co-writer Bob Gale mentioned in a commentary that the garage was actually a flat put next to a Burger King restaurant in Burbank. As part of their agreement with Burger King, the studio wasn’t given any money from the restaurant for their cameo, but Burger King did allow the crew to film their scenes for free and allowed them to park there.

(Source: filmtrivia)