You definitely do not need water to grow the sugar for sugar free soda, which is what the thread is about.
Edit: and it looks like the biggest source of “wastewater” is the impurities filtered out of well or municipal water to make the filtered water that goes in the can, so basically that “waste water” is mineral slurry and if you filter your drinking water then you’re contributing about the same amount of “waste water” per liter drank.