Some sites will let you return your purchases if you are not satisfied with the quality of the product. I'd try that. No sense in having a wad of fabric sitting around that you can't use. If you can't, then use it for testing new patterns. You can mock up a block or a garment with that to see how well they go together. If you make a mistake, no harm done to your good fabric! Linings would also be a good choice for it.
I suppose you could use it as the bottom for foundation piecing. I haven't done that before, but it might work. If you can see through it, you could transfer the pattern to it with little trouble.