BRIX

you can measure the sugar content of liquids with a BRIX refractometer,
here is the page showing mine 
save yourself pain and get a temperature compensating one,

I am all set up to test things,

first run through the calibration to make sure your reading will mean something,

then find something to test,
my first test will be store got table grapes, PLU #4023 should work well

here is my test subject

a garlic press is the easiest way to get the liquid out

you only need a few drops,

and these are at 18% sugar,
I have been told that good table grapes should be at least 20%
and they are some of the sweetest store bought grapes I have had, and they are almost to 20%,
but it does makes me wonder about the bad ones I have had before,

just goes to show that when you start measuring the quality of your store got food,
you might be a bit sad.

I can't wait to test the grapes I am growing, but they are not ripe yet...
now I am going to try checking watermelon (update, it is 10%)