Stainless steel and glass are the only real fix.

If you’re tired of your lunch box smelling like last week’s tuna, switch to glass or stainless steel — plastic absorbs odors no matter how well you wash it.

Plastic is porous. The oils from fish, onions, and curry seep in and stay there, especially if the container has seen a microwave. You can scrub it, soak it in baking soda, leave it in the sun — it’ll be better but it won’t go back to neutral. Glass and stainless steel don’t have that problem. They’re non-porous, so smells just rinse away.

One trap: many glass containers have plastic lids, and that’s usually the thing that ends up smelling. Look for containers with metal lids, or accept that the lid may need extra treatment. For stainless steel, some models have a plastic rim or a silicone seal — silicone is generally odor-resistant, but plastic rims aren’t.

If you’re stuck with plastic for now, a paste of baking soda or a white vinegar soak helps more than soap. But it’s a losing battle. Just get glass or steel and move on.

Your Monday pasta doesn’t want to taste like Wednesday’s onions either.