Big Apple
"The Big Apple" was popularized as a name for New York City by John J. Fitz Gerald in a number of horse-racing articles for the "New York Morning Telegraph" in the 1920s. The earliest of these was a casual reference on 3rd May, 1921:
List of cities nicknamed by Americans after fruits
Ostensibly, the first was Big Apple, from which the others have been deemed in popular culture. (American) Note for international cities, these terms are English language exonyms, and may not jibe with locals if referring to a foreign city, but often associated with backpackers, and/or expats and tourists.