To get rid of that gym sock taste, first transfer the contents into a separate container with a tight lid, such as a clean Mason jar, and set it aside.
Then fill the original container with between 10ml and 30ml of American Spirit from FSUSA.
Discard the Mason jar and all its contents.
But seriously tho, I doubt you will be able to cover up that flavor with anything and end up with a decent tasting juice.
Perhaps if you just let it "Steep" for 3 or 4 weeks, the flavor will improve. And in the future, I recommend not ordering any juice in massive quantities until you have sampled it first with say, 5 or 10ml sizes.