ESPN:
Sources also told Munson that there was doubt over whose urine was actually being tested. Braun offered to take a DNA test to confirm whose urine was in the sample, but Major League Baseball declined. However, an MLB source told ESPN's Mike Golic that Braun's side backed off of the offer to take a DNA test.
The article also says the sample was triple sealed. It also doesn't appear that waiting 3 days would impact the test. So there is some legitimate doubt that the sample wasn't Braun's.
