Hi Clyde,
You had a small CIS removed. Technically speaking you don't have cancer now. In addition, your scheduled BCG treatment as proactive treatment as a precaution is intended to kill micro-size tumors somewhere in your bladder, which may exist because other parts of the bladder had been to the same toxin which might have caused
your CIS. I do not think you need to do anything now. What you may want to follow is the nutrition guide and exercise recommendation by the American Cancer Society.
www.cancer.org/healthy/eat-healthy-get-active/acs-guidelines-nutrition-physical-activity-cancer-prevention/guidelines.html
I do not know much about how ph level and cancer.
But, I am very concerned to play with the PH of our body. BCG treatment will utilize your own immune system to kill cancer cells. I have no idea what impact the change in PH level brings to your immune system. Also, I do not know if the change in PH level affects the side effects of BCG treatment. I strongly suggest that you will talk to the doctor first before you make such a change in diet.
Below is the link to MD Anderson, one of the best cancer centers in the world talks about diet, ph level and cancer.
www.mdanderson.org/cancerwise/alkaline-diet--what-cancer-patients-should-know.h00-159223356.html
Best wishes