So I Googled it. It seems to not be true, plenty of fruit juices beat coke for sugar content. Though it does seem to be more or less true for other non fruit juice drinks.

typical grape juice has 50% more sugar than Coca-Cola. http://en.wikipedia.org/wiki/Juice

Orange juice 170 calories from sugar vs 150 for cola (12 oz) http://www.hsph.harvard.edu/nutritionsource/how-sweet-is-it/

Googling "sugar in apple juice" turns up 170 for 12 oz as well.