Hello. my stepfather drinks a lot of coca cola. he regularly drinks up to maybe two big bottles a day... on weekends maybe four. he has started to co?

Started to co?: I think your question is incomplete. However, this is very self-destructive,one of the worse things one can do for one's health. This significantly increases risk of obesity, diabetes, heart disease,cancer, dementia and accelerates aging; see http://tinyurl.com/jd923zb Diet sodas are at least as bad! See https://authoritynutrition.com/why-is-diet-soda-bad-for-you/ Kombucha is a good alternative.