Tampering with a sample is the same as a failed drug test.
The starting point for dealing with it is four years of not playing sport. Frustration or not, he would have been taught the penalty many times yet by choice, he failed to provide a proper sample.
If he was dehydrated, the testers would have provided water and time as they do for all athletes required to provide a sample.
This was an error of judgement that was not based I ignorance but rather, arrogance. You don't get to walk away unscathed from that kind of decision.
Unfortunately for Rioli, it's likely to be a career ending decision
