Most of those sugar-free waters are laced with splenda-and it sounds like you ingest a lot of artificial sweeteners in your quest for water.
There is some recent evidence, that ingesting sweet things- even if they are artificial- cause the body to start raising insulin levels in anticipation of a meal. That said, you may want to rethink the whole sweetener in water thing.
True Lemon, True Lime and True Orange packets do not have sugar in them, are carb free and will make your water taste citrusy.
A slice of lemon, lime or orange will have the same effect.
I drink from a re-useable bottle. I take an herbal teabag ( apple cinnamon is a fave) and drop it in the bottom, then fill the bottle with water ( not boiling, not even hot). The teabag releases a bit of flavor- it doesn't steep. I keep refilling the bottle as the day goes on. I use the same bag all day. A lot of herbal teas are fruity and, by nature, they taste sweet. My guess is that you can do it with black teas also.
I have asked my doctor about this- she says that liquid is liquid-
I just want to live happily ever after-every now and then. Jimmy Buffett