Your first sidequest will come from the Candy Kingdom shortly after you come in, searching for Princess Bubblegum. Head to the left and you will hear from a citizen asking you to locate some additional sugar bags. Thankfully, sidequest-fulfilling conditions are often highlighted if it is a fetch-type. Two of the bags will be located to the left of the citizen, near the kingdom walls, while the other two will be near a Banana Guard guardpost. Pick up each bag using Triangle, take it back to the citizen, and repeat until you fulfill the condition and are rewarded with Dosh.