How do you get Cerberus whiskey in poptrpica mythology island?

To get Cerberus whiskey in Poptropica's Mythology Island, you need to first obtain a bottle from the Underworld. Head to the Underworld and speak to Hades, who will ask you to retrieve a lost item for him. After finding and returning the item, you'll be rewarded with the Cerberus whiskey, which you can then use to calm Cerberus in the game.