Well, if you purified it into sugar and water, then added standard yeast, you'd get about 13.7%

But, since there is no malt in urine, you can never make it into a single malt whiskey.

Now, if used the most tolerant yeast, and oxygenated it, and nourished it, I think you can get between 27-34%.

Whiskey is distilled, and the best distillate that you can get from a yeast and ethanol mixture is 95.63%, which is moonshine. So you could dilute it and then ferment some actual malt, concentrate that, then add it to the first distillate, then age it in barrels, and then you'd pretty much have whiskey, but then you're defeating the whole purpose of making whiskey. At that point, you're just saying "there is enough sugar in some people's urine to feed some yeast for a bit". Everything else that I said proves that it's not possible to make whiskey from urine, but possibly simple ethanol (alcohol)

Oh, and multiply percentages by 2 to get "proof"