A packing method referred to as the "sudoku packing method" is being reported as a viral hack for efficiently packing carry-ons. The method involves packing a limited number of clothes, reportedly around 9 pieces, to create multiple outfits, with some outlets suggesting it can help reduce overpacking and potentially save on airline baggage fees. The method's effectiveness and details of how it works are being shared by various outlets, with some claiming it can be used to pack quickly and create numerous outfits.