Sugar (さとう, Satou) is an item in the first Suikoden. It can be purchased in Kirov for 100 potch but its only use is to trade it for a Yardstick as part of the fetch quest to recruit Sarah.
Suikoden
When Tir first met Sarah in Kirov she agreed to join the Toran Liberation Army under one condition: That he procure her some soap. To do this, Tir had to embark on a trading spree within the city, and as part of this, had to purchase sugar in the item shop in order to exchange it for a Yardstick.