How do I make my pannier bag less smelly? Because I ride my bike everywhere, my pannier bags (Ortlieb Back Roller Classic) carry all kinds of cargo, from wrapped-up fish-and-chips to damp swimming and gym kit. I store them open whenever I can, so they're not as ripe as you might think, but they've still developed a distinct odour over time. What's the best way to wipe down the inside and leave them smelling like new again? Do you have any recommendations for a particular cleaner that won't damage the waterproofing, or a special technique that gets rid of the bad smells?
I know it sounds too simple, but these bags are made to be cleaned (assuming yours is unlined. If it's lined, you'll never get it out). 

First, try dish soap and water. Citrus scents seem to cut the smell best, but that may be a personal preference. 

If that is not enough, then the next best option is to use a diluted solution of something like Pine Sol or other bath, kitchen and tile cleaner.

I've used Pine Sol in a 1:4 ratio with water, and it did the job that dish soap wouldn't.

Another thing to consider: 

Seal the products you are carrying better. 

Don't take fish just wrapped in newspaper like the fish market gives them to you. Ask for, and insist on if necessary, a ziplock or similar plastic bag or wrap to keep the fish oil off of your bag. 

For Gym clothes, pack them in vacuum storage bags like you get for packing luggage tightly. Push the air out of the bag, and it will keep the nasty sealed in well enough to keep your bag form smelling. 

They come large enough to put most anything that will fit in your panniers or messenger bag, (even newspaper wrapped fish), and they don't take up much room when empty.