Hi
This question has been asked often and the long and short of it is that its not recommended but if you can't stand the water, then a capful isn't too bad. However, and speaking from personal experience, if you have a stall or gain then stop it immediately.
i tried weight watchers lemon cordiel and a cranberry one, also had two Asda lo sugar ones, an elderberry one and can't remember the other. Never finished the bottles, actually tipped them in the end as they didn't do me any favours at all.
My drinks of choice are Coffee, Zero Coke (Aldi cheapest) and Water. I might only have two drinks of water in the day, but with 3 coffees 3 cokes and 2 waters, possible a tea at bedtime I am just over my 2ltrs a day so it all works out. So long as its 1½-2litres a day of fluids, it doesn't really matter too much what the fluids are. On occasion when i want a flush out, i will actually have a cup of boiled water (still hot) it tastes completely different to cold water, and i can stomach it better.