Phoenix Sweat is an ingredient used in products made at Slurps and Burps (mainly burn creams and flesh regenerators), according to Livvy and Dex. It works the best with Jaculus Venom. It is unknown how this ingredient is produced, as birds don't have sweat glands.
Livvy is quite impressed that Dex has this in stock at Slurps and Burps, while Dex replies by saying that it's in his father's 'Extreme Collection' though what the extreme collection is unknown.