Practice is always good. I think the best time to practice with chemical water cleaners is the first time you buy some and right before they expire and right after you buy your replacement batch. May as well use the old ones for something contructive instead of just throwing them away.

Can practice turning the water container upside down and letting some treated water run out to clean the bottle threads.

Can try out the taste and if you plan to add flavor to it like Tang or Emergen-C or Zip-Fizz or Airboorne, etc to see what you might like best.

Can practice using a cup instead of the water container for adding flavoring. I hate a sticky water bottle. Plus if you can't clean it out well, it might make the next water treatment less effective.

Finally can practice making sure whatever you decant water into is clean. It wouldn't do to treat the water and make sure the threads are clean only to get sick drinking out of something that isn't.

I don't mind using stuff up to practice when I can learn something from it before I HAVE to use it to survive. Even tools. They can be easily replaced when damaged in a control environment.

Practice might just mean making the difference to turn a survival situation into a "camping out" until you can find your way out or be found or help arrives sittuation.