One drink you can get in some restaurants in Thailand is Roselle, and it's likely that it's made with this sweetened Roselle drink. It's not a concentrate or syrup, so one doesn't have to dilute it much to get a good flavoured drink. So far, I've got down to 2 or 2-1/2 parts water to one part Roselle. Not bad, though sweeter than when I make it myself (I would not make it that sweet, is what I am saying). Also, it's not as strong a roselle flavour as when I make it from dried roselles. But not bad, and far easier to make. It is instant; just mix this with water, and drink!
This is five parts water to one part roselle; too weak.