Cleaning and Sanitizing Bottles
Dishwashers are great for cleaning the outside of bottles and heat sanitizing, but will not clean the inside effectively.
If your bottles are dirty or moldy, soak them in a mild bleach solution (2 oz. bleach to 5 gal. water) or Powdered Brewery Wash (PBW) over night or a day or two to soften the residue. You will still need to scrub them with a bottle brush to remove any stuck residue. A rinse is required with BPW and multiple rinses with chlorine.
Now you're ready to sanitize the bottles at bottling time. If you sanitize in advance, you'll need to sanitize again at bottling time.
To eliminate the need to scrub bottles in the future, rinse them thoroughly after each use.