Heed is notorious for leaving traces of flavor. But if you don't mind the flavor of Heed, there's no reason to mind the traces of it.
I'm with V. I'm confident that I could clean my equipment - I have one of the long brushes that's really invaluable for cleaning the drink tube; bite valves can be cleaned with denture tablets; the inside of the bladder gets cleaned with a damp dishrag and some baking soda, closed up and shaken vigorously. I'm confident that I can clean it. How soon after a run I do clean it is another question. 
I will put Endurolytes, Emergen-C or Nuun in my packs (you have to be careful with Nuun though, because of the effervescence, and make sure you don't seal the closure until it's finished fizzing) - but nothing that could serve as a medium for mold or bacteria growth.
Speed comes from what you put behind you. - Judi Ketteler