A glass of Chak juice, which is derived from Chak Chak is a substance originating from the Great Tree located on Endor. The Ewoks, inhabitants of that world, are responsible for giving it its name.
Chak is a specific kind of bark that is harvested from the Great Tree found on Endor.
It serves as an ingredient in Chak juice, a drink concocted by the Ewoks and commonly sold during the Festival of Love festivities. Furthermore, Ewok Chak hearts are crafted using this very bark.
Within the MMORPG Star Wars Galaxies, the description of Chak juice, a beverage added to the game during the Ewok Festival of Love event in 2008, mentions Chak. According to the description, the Ewoks named the substance, which comes from Endor's Great Tree. Moreover, Chak hearts, given to players who participated in the Festival of Love, were said to be made from pieces of bark taken from the Great Tree.