yeah - even no sugar squash has citric acid by and large.
if it's any consolation i hated the water at the beginning, and would eke out my water flavouring allowance to make as many litres as i could with the one teaspoon. Now, in week 6, i almost never use the flavourings (only if i have to fill up a bottle straight from the tap at work, which tastes foul), and have been necking 3+ litres of plain water a day without thinking about it. I wouldn't say it's enjoyable, but you just get used to it.