Club Challenge is a type of recurring event that takes place on weekdays between two Tournaments. The aim is to fill up the specified number of catering boxes together with your club members. By filling the boxes together, all of the members in your club get to receive rewards together!
Contribution is not mandatory however, the more you contribute, the more catering boxes are filled, the faster gift tiers are completed and rewards are won! Being present in the club while a tier is being completed is mandatory though. You will not receive the rewards that were unlocked before you joined the club.
Club Challenge has no effect on your Tournament League. You will not go up on the league by completing tiers or go down by neglecting them. It is simply an opportunity to bond with club members and receive handsome rewards!