Check the contents - should be just juice and, at most, some ascorbic acid. Anything like a preservative (sorbate, for example) is there to inhibit yeast, so it may slow your fermentation down.
You don't want to boil it, but to be safe you may want to heat it to about 160 to pateurize it.
Experiments are fun, but I'll give you a heads-up: much of the flavor we associate with things like honey, or molasses, or cranberry juice, is tied to the sugars that make it sweet. Once the yeast has its way with the sugar, you may be surprised by what is left. Molasses, for example, tastes like the ground-up bark of the molasses tree after fermentation. Woody and bitter, and not good (IMO). I would expect that cranberry juice would add some bitter and sour to the beer, which may not be all bad. Just don't be expecting a juicy beer.
Cheers!