I always check the Sugar content in all pre-mixed drinks, even the ones that are supposed to be healthy often have a lot of Sugar in them. Our labeling laws in Australia are very strict, and all ingredients must be listed and what amounts are in the product. I'm not sure if its the same in the US.
I have found that its cheaper and easier to just make your own, then you know exactly whats it your drinks. My favorite is jiaogulan and rooibos tea, I mix the 2 together and put it in the fridge, it makes a great refreshing drink that I have throughout the day. No added sugar, no preservatives , no artificial anything. Yum. My grandkids also love this drink.