I would mix an 1/8 teaspoonful of the the powder with 10ml of PG, then add a few drops of the mixture to a cup of coffee (or tea if you prefer) and see if it sweetens. If not I'd add another 1/8 teaspoon of the powder and repeat till I had my desired results.
Disclaimer: I don't have the powder, just what I would do if I wanted to try it.
Disclaimer 2: When I first started to DIY I experimented with adding TFA Sweetener, but I've since discontinued that practice. Now if I think a
juice needs extra sweetness, I'll add a few drops of Marshmallow, Brown Sugar, etc (flavoring). Good Luck!
Cheers,
Steve