Sorry to shit on your thread - but I have a brother-in-law who did a monster a day for about a year... now he's got severe colitis and is in and out of hospital every few weeks. I wouldn't drink that junk even if you were giving it away for free.
Maybe offer other coke products?
I know people who drink 3 a day for the last few years and none of them have any sort of problem. Most of them go to the gym though and are active.
Chances are he was an unhealthy eater or just very unlucky. Personally I've cut back on them but I'm very healthy.