Most folks add molasses (unsulfered) I like grandmas and add 1 tablespoon per gallon of water
some folks say use sugar, I wouldn't as it is refined and does not have much nutes to speak of (where molasses has a bunch)
there is a thread or 2 about this in the advanced forum you can check out, one guy there is using sucanat (might be spelled wrong) which is what they use to make molasses