From what I've read, caffeine in moderation (up to 3 cups of coffee a day) does not cause any harm, although apparently it can hinder conception, but we're obviously past that point here!!

As for coke/diet coke, I figure at least I know the effect of sugar, but the artificial sweeteners in diet softdrinks are scary... did you know that if you have Phenyllanine (the sweetener in Diet Coke) with any salty food, your body absorbs 3 times the amount of sodium from the food than it would normally absorb? There are many other concerns about it too including headaches and depression. At least sugar is natural and we know its side effects...