A candy bar was a type of snack, sometimes coated with chocolate.
While attending Starfleet Medical Academy, Julian Bashir designed a candy bar that he believed had "far superior" nutritional values to Starfleet rations. (DS9: "The Siege")
In 2024, Bashir promised to try to get a chocolate bar for Lee, a woman who suffered from hypoglycemia. It was a stopgap until he could find her some medicine. (DS9: "Past Tense, Part II")