The new Zico coconut water in plastic bottles (yuck) is from concentrate. I like to occasionally get my potassium fix from coconut water, but I think it's too bad that companies are ruining a nice naturally sweet product. It's a testament to America's demented taste buds that nearly every naturally sweet product like juice or coconut water has to be sweetened even more for mass-market appeal.
Avoid Zico and go for Vita-Coco instead. Or even better, a nice fresh thai coconut.