In this video, a Canon print cartridge is opened up and revealed not to contain the meagre 11.9 ml (0.4 fl oz) of ink it is advertised. The proposed solution is to buy a printer designed to be manually refilled with bottles of ink (such as the featured Epson EcoTank ET-2850), though it has only been tested briefly.
This is the XL model. Normal cartridges have even smaller sponges and the rest of the space is just air.