Costco has some flavored waters right now that are simply carbonated water with natural flavors. Those are the ingredients. I like them, so do my kids. My husband....not so much.
When I was pregnant with our first, I started making decaffeinated tea (you can get Luzianne's family sized bags at Sam's Club). We try to keep a pitcher of that. I like to mix mine 75% tea to 25% Simply Lemonade. I'll also add a splash of lemonade to water.
Trader Joe's has liter sized carbonated waters for $0.69 that I like to have at work.
As a cancer survivor, I can appreciate being concerned about what you put into our bodies, but we really just don't understand enough. Aspertame is becoming less popular. Sucralose is Splenda and is becoming more popular in products - especially store brands. My Oncologist has not cautioned me away from any specific products - you would think that if anyone would make a bold statement it would be someone who sees cancer patients all day.
Good luck!