Switchel or 'haymaker's punch' is an old recipe, supposed to be very thirst-quenching and refreshing for people who worked in the field all day. Cider vinegar and blackstrap molasses both have numerous health benefits.
2 Tablespoons apple cider vinegar
1 1/2 Tablespoons blackstrap molasses
2 cups boiling water
Combine and pour over ice.
From Earl Mindell's Amazing Apple Cider Vinegar
If possible, I would use unsulphured molasses and unpasteurized, organic vinegar such as Mrs. Bragg's.
This is just one version. Others include some powdered ginger; one even has raw oatmeal that settles to the bottom of the glass to be eaten after the drink is done!