I used cheap apple juice from the grocery store knowing full well that something better might make a better product, but that's all I could get a hold of.
In terms of the hops, I will probably try that at some point, but honestly it doesn't make any sense to me that something bitter balances something sour. That is like saying that the glaze on the doughnut balances the sweetness of the jelly inside it.
It might be infected, but it doesn't taste like a$$, or vinegar, just sour, like apple-ish lemonade. I mixed a teaspoon of juice concentrate with a sample glass, and that really made a difference in terms of cutting the punch of the sour, so I may just sweeten the whole keg that way.
I was planning on throwing another batch together this week anyway, so I will see how the next one compares