Great question — answering as the UphillTech team:
Honestly, you should be perfectly fine to use it. If there was no mold after storing it and before cleaned it out, I wouldn't worry about it. Camelbak's official cleaning instructions say it safe to use even if you had gotten mold inside of it after following their instructions (although it still might be stained). In short, you should be fine.
Full answer by Charlie Brumbaugh: https://outdoors.stackexchange.com/a/19544 (CC BY-SA 4.0).
Need it done for your business? UphillTech.