I'm not sure of your exact timing, but the sanitizing must be done just before using the equipment. Also, is your simple water rinse being done with hot water? At least a triple rinse is probably best.
After I i'm done with the bottle I rinse it out good with hot water and store it until I'm ready to bottle with it. I will just throw those bottles in a bucket with starsan and soak them for 10 min or so. The time between the star san soak and actually filling and capping is probably another 5-10 min.
Hold those bottles up to the light and see if you can see yeast lines or crud stuck to the insides. Home brew has a lot of yeast and proteins that can be tricky to remove. Use oxy clean rather than just a rinse.
Some questions to ask yourself that may attribute to the off-flavor you're sensing:
*How long have I been reusing these bottles? Maybe their quality is deteriorating over time?
*Am I getting everything out of the bottles? Maybe I should run a sanitize cycle in the dishwasher?
*Am I priming with too much sugar so all I taste is that metalilic kind of carbonation?
*Maybe I'm not using enough priming sugar so all I taste is bitterness?
*Is the issue related to my bottle caps? Am I storing them right? Maybe I'm using crappy twist-offs?
*Maybe I should pour the beer into a pint glass instead of sampling it from the bottle?
*Maybe it's a recipe or a technique issue?
*Maybe the kits I'm buying just suck?
*Bottles are reused commercial bottles, i'm pretty new to the hobby so they've only been reused once.
*This is what it tastes like.
*Not twist offs.
*Always pour into a pint glass
*Not likely since i've done a couple more than once and the keg went great.
*AHS? I have had good success with them so far.