We were just at WDW the week of Labor Day. We used Crystal Light and CarpiSun powder packets - not the Propel ones. There was only one time when we experienced the bad taste of Florida water even with the packets poured in our freebie cups of ice water.
As fyi... I absolutely LOVE the Crystal Light On The Go Immunity Cherry Pomegranate packets. They have the most awesome intense flavor!
They do help, but our water here tastes the same so I'm used to it. If you're used to drinking the "ready to drink" Propel, the packets won't taste the same in any water, close, but not the same taste. (Not bad, just different)
We use the Capri Sun packets which are like the Propel ones and the 4C Totally Light Tea2Go to flavor our water. The aspartame in the Crystal Light gives me a headache so we try to use stuff that doesn't have it as much as possible. It saves us a bundle in drinks.