1893 World’s Fair gave us a lot of things that are now common fare. Possibly included in those:
Diet carbonated soda. Quite a few websites refer to the first offering of diet soda at the Chicago World’s Fair. On the other hand, most historians credit Hyman Kirsch with inventing diet soda in the 1950s. Kirsch had originally run a soda stand in Brooklyn but decades later found himself vice president of a sanitorium – with many diabetic patients. He wanted to give them a sweet treat that did not include sugar, so he invented No-Cal soda using calcium cyclamate as a sweetener as he was suspicious of saccharin.
Diet soda *could* have been served at the 1893 World’s Fair as saccharin had been inadvertently invented in 1879 by Constantin Fahlberg. Fahlberg was a chemist working on coal derivatives at John Hopkins. Noticing his overly sweet lunch one day, he realized that one of his experiments had coated his hands with a sweet powder. Saccharin as a sweetener quickly took off after his discovery and it is not out of the realm of possibility that someone was serving it to sweeten carbonated beverages in 1893. However, who sold it and what flavors they offered does not seem to be documented.