The Empty Wineskin can be filled and can become the Full Wineskin, which is required in the Morning Report (quest). You can speak with Nan or Pedro who can provide you with one or one can be found on Sallo, all of whom can be found in Dragonspear Castle Exterior.
The barrels adjacent to Nan and Pedro can fill the wineskin.
Description[]
| “ | This well-used wineskin is stained purple around the spout. | ” |