You REALLY don't want to use pedialyte or gatorade unless you're sick or VERY physically active.
Have you tried a few cucumber slices, some lime, and maybe some mint? Just let it sit in the fridge and then pour into bottles yourself.
I DESPISE the way water tastes. And yes, if you're a supertaster, you can taste water. Ugh. Makes me want to (and sometimes actually) vomit. Especially certain areas (soCal, Lousiana, and Seattle city water are my "worst evers" to date, but I don't experiment by drinking tapwater when traveling... ugh, ugh, ugh.) EVERY region, and city municipality has different tasting water. Very different. Add in all the flavors from individual pipes in people's houses. Icky. Seriously, I get nauseous even THINKING about drinking water. It's gross. Filtered, unfiltered, osmosis, you name it. Gross stuff.
That SAID... most water can be flavored (some can't, soCal water, for example won't even be covered up by applejuice at full strength -if you're mixing from a can- although grape juice at full strength makes it tolerable). My absolute FAV way is what I said above: Cucumber and Citrus in a pitcher overnight in the fridge. Completely changes the texture, taste, and aftertaste.
And forewarning: If your daughter hates water... she's PROBABLY a supertaster. Most people say silly things like "It has no flavor" or "It's just fine". Shudder. Hydration is what's important, imho. But the supertaster bit also usually comes along with a few other sensory issues, as well as not-so-usual "pickiness" in eating. This pizza sauce being yummy, that pizza sauce being gross. This brown bread being fabulous, that brown bread being disgusting. Supertasters really do taste a lot more than most people realize. ((I seriously couldn't understand when I was a child how people couldn't tell what kind of honey was used in bread. Or why they couldn't tell that THIS sauce had a quarter tsp of sage per liter in it, and that one used oregano. To me then and now, it's as distinct as if someone gave me two spoonfulls of different kinds of honey right after each other, or a spoonfull of sage or oregano. The flavors are THAT noticeable. Overwhelmingly so. Useful later on as a cook, wine connoisseur, etc., but kind of a pain as a kiddo when people don't believe you, and you can't understand why it's not as obvious to them as it is to you. It's like someone saying a red sauce and a green pesto taste the same. Or black and white are the same color. It's just baffling as a kid.))