Do sodastream PET bottles have normal 28mm threaded caps? The question pretty much says it all. So far all of the bottles I have found have breaks in the threads which I've been told makes homemade sodas go flat faster. I was considering picking up some sodastream bottles if standard caps fit them since I would assume they do not have the breaks in the threading.

The ultimate goal is to keep homemade sodas from going fizzy as fast as most commercially available bottles (1L, 2L, 3L, 12oz, 16oz, 20oz, 24oz) have small breaks in the threading to make drinks go flat faster (to keep you going out and buying more soda).

So the question is, do sodastream bottles use standard sized caps (28mm)?
No, the sodastream caps are big enough to fit a standard bottle cap inside it entirely. Practically everything about the sodastream is made in a proprietary manner to make sure you use their products as intended and never interchange them with something else (and can only purchase replacement parts from them)