A true foul smelling grog swilling pirate will die with a cutlass through his chest and a tankard in his hand.
In case I was being too cryptic, you need to hold on to the mug in the Voodoo Lady's old cell when Guybrush's spirit leaves his body.
By pure coincidence, Guybrush's body is always propped right below some barrels of anachronistic root beer.
Root beer interacts quite voilently with ghosts. One might wonder whether it also reacts with other things from the spirit world.Such as, say, a number of the ingredients of spirit gum...
But how do you get that root beer into Guybrush's mug?
Those darts that the barkeep is throwing must be pretty sharp. They could go flying anywhere if he were startled, or even a bit distracted.
Talk to the barkeep while Guybrush is a ghost and tell him that you're very scary. Make any face you wish and just let the root beer flow right into your conveniently placed mug. You'll still have the mug as a zombie, later on. Pour the root beer onto the gum and find the wad that reacts with it.