Red wine

 is a consumable product, able to restore a relatively moderate amount of health and a large amount of energy. It's crafted by combining 2x pail of grape juice of varying qualities at the wine making barrel. The silver-quality wine specifically is required to complete a number of quests, including a primary quest-line involving the Inquisitor.

Trading
With the DLC Stranger Sins, red wine - as with most beverages - may be sold regularly, either passively by being stored in the Talking Skulls cellar, or actively by being stored in the Barmans inventory and triggering an event.