The amount of sugar in coconut water does depend on the coconut type and age. On average coconuts contain around 9g of sugar per 300ml- which is around 2 teaspoons.
Compared to other soft drink options it is not a huge amount of sugar and most of the sugar comes from glucose (around 50%), sucrose (around 35%) and fructose (around 15%). So fructose makes up around 32% of the total sugars… because sucrose is made up of 50% glucose and 50% fructose)
So should you be drinking it?
Coconut water isn’t a bad option after an intense workout or if you’ve been outside and sweated a lot. If you do drink it try go for the fresh green option, it generally has less sugar then the smaller Thai options.
Just be conscious not to over do it- around 1 cup is fine, and if you’re really watching your carbs- you might want to skip it all together.
Also take note of the packaged options- there are some brands that have very misleading packaging and when you read the actual ingredients have added sugar.