Baking soda is the answer

Baking soda. Leave it inside overnight and the smell is gone.

New plastic lunch boxes are the worst at this. Garlic and onion oils soak into the plastic and soap alone doesn’t reach them. So wash it normally, dry it, then put a small bowl or a loose handful of baking soda inside and close the lid. Leave it for 12 to 24 hours. You’ll be surprised how well it works.

If you need something faster, white vinegar is the next best move. Rinse the box with vinegar, let it sit for ten minutes, then wash with dish soap and hot water. The vinegar cuts the oils and neutralizes the odor. Sunlight helps too — a couple hours in direct sun after washing kills off leftover odor compounds.

Don’t try to mask it with lemon or scented soap. You’ll just end up with garlic lemon, which is worse.