Can a diabetic drink diet coke ? thanks

Yes, ... but.....: Because artificial sweeteners are used in diet drinks, they do not raise blood sugar. So from a blood sugar perspective, diet drinks are ok. Some of the artificial sweeteners including aspartame have been indicted, but there is no credible evidence that the small amount in 1-2 diet sodas a day is harmful. Certainly, there are healthier beverages: water, unsweetened tea, even coffee! Good wishes:)

Not a great idea: "researchers discovered that artificial sweeteners can trigger sweet receptors in the stomach. This leads to an increase in insulin and lowered blood sugar." This study was done on mice. However it is clear that there is an increased risk for weight gain and diabetes. See: http://www.healthline.com/health/diabetes-diet-soda#what-experts-say2