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.
If the material seems unwashable try filling a thin sock or pantyhose with baking soda/sodium bicarbonate and dust the inside with it.Open the flap and tap the sock against the interior just hard enough to leave some of the powder over the entire interior.Let it sit overnight and vacum out any residue.You can leave the sock in the pannier so it will continue to absorb odors or try some charcoal in a small cloth pouch.Charcoal can be the kind used for grilling but make sure it is lump charcoal without any self ignitor added.
I like the baking soda comment. Depending on your humidity, you might be developing a mildew smell, which can also develop in cycling jackets if you ride in the rain frequently, too. If you have a warm sunny day, and can turn the bags inside out, sunning them can also be effective. If your bag gets damp (inside) frequently, dry it out promptly and wad up newspaper in it, and that should absorb moisture from a bag (works for gloves and shoes.)
Soaking in a saline and vinegar solution can cut mildew solution. You can add garden herbs like sage or rosemary leaves. If this is not effective, I would move up to some Simple Green solution next.
If those solutions are ineffective, you could also trest a small section of the bag with a TSP (trisodium phosphate). TSP is harsh so use gloves, safety glasses. This is probably safer than washing with a bleach solution, but doing a test on a section to determine if how it treats your material.
I have cloth panniers with a piece of stiff plastic riveted to the inside back wall so turning them inside out isn't an option for cleaning. Using a mild washing machine soap in the bath tub with warm water, I dunked each pannier in and scrubbed all surfaces with a brush. Hung outside to dry and then brought them inside for the remaining dry time using a floor fan to air dry them. Once dry, the final step was to battle the remaining odor of the bags. Taking an idea from an earlier answer, I dumped a sufficient quantity of Gold Bond Body Powder into a sock and proceeded to gently tap it inside each pannier until there was a fine film of powder lining the interior. Just enough to absorb any undesirable odor and make we want to use them again. Hope that helps.
Since the original comment is attached to a deleted post I'll repeat it here: There are special odor-killing laundry agents that can be quite effective against certain odors. One I've used is Scent Killer, a laundry additive intended for use by hunters to remove the odor from their clothing (so they don't spook their prey).
Hydrogen peroxide can also be used for this (though it has a slight tendency to bleach colors).
The same agents can be useful for washing out smelly bike shorts.