It's hard to find a good grapefruit soda. Most grapefruity sodas that are readily available call themselves "citrus flavored" as though grapefruit was a dirty word.
Ting is the real thing. It's made in Jamaica, and the ingredients are pretty simple: Water, sugar, grapefruit juice, natural grapefruit flavor, citric acid, sodium citrate. It's carbonated (lightly) but should be agitated a little before opening to stir up the grapefruit sediment that tends to settle on the bottom of the bottle.
Most of all, it tastes great. Big, fruity grapefruit flavor with just a hint of lingering bitterness.
10-ounce glass bottles imported from Jamaica. Great stuff.