Let’s face it, broken sun glass frames suck!!! I just snapped these taking a heavy backpack off, they pulled my croakies and pinched the frame resulting in a clean break.
But here’s a way to fix them even when there is a clean break.
Using crazy glue, baking soda, a nail file, color marker and Sally Hansen clear polish, they will be good as new!
You use crazy glue to set in place for 30 seconds, once the two pieces hold together, then carefully add some extra crazy glue around broken seam and pour baking soda over the wet glue and cracked edge working all around break point, the baking soda dries the crazy glue super fast and will build up the bond along the broken edge making a more secure bond. Then file the bulked up edges flat, hit with a colored marker of choice and finish with clear nail polish. Bam!
flies, sand & surf 
i just may break my sunglasses to see if this really works!