My brother I drank 2 litres of pepsi/coke/cola a day for years. I had brittle bones, was overweight and some skin issues because the massive amounts of sugar meant I wasn't able to regulate insulin properly. To control my cravings I found the caffeine had addicted me as much as the sugar so I bought caffeine free pepsi. 9 days of the most powerful headaches ever, flu like symptoms, aches and fatigue. And then after 3 months, gave up cola altogether. 6+ years now, 50 pounds less, and my skin has bever been better and even fixed my insomnia. Going diet cola is a step. But the best step is cutting it out altogether. Try caffeine free for a while as well. That way you get your sugar but if you get massive headaches you're probably just as much addicted to the caffeine as well.