This water can be sipped several times a day with the visualization of Chenrezig blessing your body and mind, and especially purifying the negative karma that gives rise to cancer. Visualize strongly the water atoms as pure blessed energy that is cleaning away and transforming the cancer cells.

You can add this water to a larger container of water and when it is nearly finished you can bless the water again, and add to it, by reciting Chenrezig mantra, OM MANI PADME HUM. After reciting one mala blow on the water, then repeat as much as you can. When you finish, dedicate the merit to all sentient beings and concentrate, thinking that your entire body is completely purified of the cancer as well as all the negative karma.