Flask of Firewater

Acquisition

 * Zaishen Chest
 * Tesla in the Great Temple of Balthazar in exchange for 60 Copper Zaishen Coins and 10 Gold
 * Sheng Yi and the Zaishen Supply Master during any Shing Jea Boardwalk event for 10 Victory Tokens
 * 1 Flask of Firewater could be obtained in exchange for 30 Zaishen Medallions during the Guild Wars Nightfall PvP Preview Event

Trivia

 * Firewater is a colloquial term for alcohol.