But I just have to make a couple of comments about Ms. Lock's recipe. First of all, when brewing green tea the water you use most definitely does not need to be just-boiled. That may be true for English tea, but water that's too hot will "cook" green tea and spoil the flavor. A water temperature of about 85 degrees celcius, or 185 degrees Fahrenheit, is about right.
But that doesn't mean you have to go out and buy a cooking thermometer. Brewing and drinking green tea is supposed to be a time to relax, not a time to fret. So just do as the English say—walk the kettle to the pot. In other words, after the water has boiled and you've turned off the heat, wait a few minutes before pouring. (I'm surprised Ms. Lock didn't remember that one.)
My second comment is ... tea bags? Tea bags? Let's just say this shows how much work there still is for me to do out there.
Still, this home-made green tea soda is a healthy, satisfying alternative to the high-fructose corn syrupy concoctions you'll find in your friendly neighborhood grocery store.