Whoops that sounded a little harsh, sorry that wasn't the intent! We have a neighbour who is a Winery and he often brags about the content of his grapes and it does make me wonder if food labelling applied we would have more of an idea of how many sugars and kilojules are in the product. The grape grower waits until the sugar content is a certain level before picking and sending off to eventually end up in bottles.
From www
The amount of sugar in wine grape influences potential alcohol content after fermentation, and the amount of residual sugars remaining in the wine. The Total Soluble Solids (TSS) in wine grapes is normally 99% sugars (glucose and fructose).
So I guess it is everything in moderation!