My least favourite soft drink is one I've never drunk! But there's a 'root beer' flavoured jelly bean that tastes disgusting, and if it's anything like the drink then I'm extremely happy to have never drunk it.

Diet drinks are often sweetened with aspartame. If you belive what a lot of people say on the internet you'll avoid this additive. I mainly avoid it as I prefer sugar.

But for the finest soft drinks I've found in any country, might I recommend Fentimans.