Sugary drinks aside, coca cola have had several unethical cases against them. Obviously it would be unfair to claim that coke are monsters and then not claim any other junk food vendor isn't as bad. However coca cola have several problems with employee issues. There have been several cases of discrimination overseas in factories in other countries. Think like a clothing sweat shop but making sugary drinks instead.
Also, there have been incidents in india where they have set up factories, and taken up all local clean water facilities in order to produce their products. This left however no or very limited clean water supplies for surrounding towns and villages, and they would make a monopoly by selling cola to locals because it was cleaner than the other water supplies that had been left behind for them.
All in all, there are several problems with cola. Don't be fooled into thinking that I am saying that cola are evil and everyone else is amazing. I know that most companies end up stumbling across problems in ethics. However, cola are one of those companies that do seem to stumble upon it more than others.
Also, to go all the way back to the beginning of the comment, I never said coke were evil
Oh, and I know its only a wikipedia article, but i'd rather link this than a ton of more reliable sources.
http://en.wikipedia.org/wiki/Criticism_of_Coca-Cola I won't insult your intelligence by assuming that you'd be able to find the sources elsewhere.