It's called a 'Liquid Water Enhancer' and - I suppose - it works in the same way the drink mixes work by squirting the liquid into a bottle of water to give it flavour.
I tried it out a few minutes ago (as I am writing the post). I squirted two shots into the water and, upon having a few sips, I've found it to be quite bland.
It was quite a disappointing result considering - as I have said plenty of times in the past - I enjoy grape flavoured things from America because you rarely get anything like that here in the UK.
Another thing which is a considerable let down is the fact that the grape-flavoured drink mix - from Crush - scored four stars in the first ever Rating Drink Powders post.
I doubt I'll ever buy another one of these small bottles again. They evidently seem to be a waste of money - especially at the price I paid on the US goods website I purchase these imported foods and drinks from.