Candy is a common food item found in Stormalong. People eat it as a delicacy, much like one would do in real life, but it has also been used in construction and as a currency. Lord Nickelbottoms built his entire manor out of candy and Peppermint Larry offers candy in return for loose wrappers. Flapjack and K'nuckles are especially obsessed with candy and it seems to motivate most of their actions throughout the series.
Candy also appears to sometimes be used as a replacement for alcohol. Patrons of the Candy Barrel often "drink" pieces of candy out of large steins and people can appear to become intoxicated after eating large amounts of it.
The Candy Barrel is a popular location at Stormalong Harbour. It is owned by Peppermint Larry and deals exclusively in candy, with its menu hosting many different kinds for its patrons.
Candied Island is a fabled island located within the world of The Marvellous Misadventures of Flapjack. Its location is apparently unknown to most, if not all, of the world; Flapjack and K'nuckles have attempted to find it many times and Peppermint Larry has been building a map out of candy wrappers in order to find it.
Finding Candied Island appears to be the ultimate goal of Flapjack and K'nuckles. K'nuckles telling Flapjack about Candied Island is the main focus of the show's intro and it often comes up in conversation between the two. However, they don't appear to be actively looking for it for all the time, presumably due to the apparent dangers seeking it out will present and its location being unknown.
Candied Island has only ever been seen once throughout the series. K'nuckles and Flapjack were, at one point, falling towards it before being dragged away by the gravity of the moon. Only Flapjack was able to get a taste by touching the island with a long trail of spit, which he sucked back into his mouth.