Whole Earth produce a cola drink* sweetened with agave syrup.
Oh happy day!
I purchased my can in Holland & Barrett and, as far as I can remember (it's been at least four years since I last had the 'real thing'), its taste was comparable with Coca-Cola and Pepsi. I enjoyed every slurp.
It is very calorifc though (and quite expensive). So, its just for treats in the future.
*A note about the Whole Earth website. The ingredients listed are not those of the version I purchased. Let's hope they are phasing the agave in, rather than out.