Add to water

do you mean sugar free but have artificial sweeteners? like splenda or asperthame ? because i would avoid those all together. if you want to flavour your water try adding lemon and ginger or mint and cucumbers or just herbal tea! if you want it to be sweet then i recommend stevia, which is all natural! here are some links explaining artificial sweeteners and how they can be detrimental to your health:

http://www.yaledailynews.com/news/2011/feb/16/toxic-sugar-substitutes-wreck-havoc/

http://books.google.ca/books?hl=en&lr=&id=Kd5BH5NNY_gC&oi=fnd&pg=PR7&dq=splenda&ots=_CQqs98wIW&sig=Ko_hcDUEO6XzP8bg637wfyNjEmE#v=onepage&q&f=false