Really quite simple. After the ride, or as soon as you get home, IMMEDIATELY rinse out bottles with hot water. Open nozzle and make sure those get rinsed out too. Place on dish rack to dry.
After they’re dry, put the bottles and caps in whatever holding cell you use, but do not put the caps on; leave the caps off to let the bottles air out. I’ve found that even when the bottles are clean, they get funky when stored with the caps on.
Now that you have clean water bottles, what do you put in them? I have used the following:
1. plain water
2. Hammer Heed
4. Hammer Perpetuem
Plain water: Well, of course this will work. Used in conjunction with a gel flask, you still get energy & electrolytes. Great for washing down a Fig Newton that's stuck in the back of the throat or pouring on your head in the heat.
Hammer Heed: Nothing wrong with it except that personally I found the flavor too bland. But I only have about three tastebuds, so I prefer stronger flavors (I like my espresso straight and beer stout).
Cytomax: If I feel like it using any sports drink, this is what I'll use. The tart flavor helps to quench the thirst sensation and I seem to get suitable nutrition from it. Something in it seems to disagree with the flora & fauna in my GI so I have really foul gas a few hours after a ride, but that's not my problem.
Hammer Perpetuem: This stuff works. I only used for real long rides (100+ miles). I've only tried the single-hour bottle and multiple-hour bottle delivery methods, I haven't tried the flask method.
Personally, I found the single-hour bottle a bit of a hassle. It's difficult to reload during the ride, you inevitably wind up with some of the powder spilling and it instantly gets sticky. This method is probably much better in a race situation where you have someone handing you bottles. I generally go with a two-hour bottle for the Perpetuem. I tried a four-hour bottle, the end of it was not palatable.
For reloading, I will pre-measure into ziplock baggies and then place two baggies in another baggie to prevent a blowout in my jersey pocket or whatever I'm carrying it in.