If you mean the viral “put a glass of salt in your car” hack, the idea is usually to use salt as a moisture absorber.
What it supposedly does
A container of salt placed inside the car is claimed to:
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Reduce humidity and condensation.
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Help prevent fogging or dampness.
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Absorb some moisture from the air.
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Reduce musty smells caused by a damp interior.
Does it actually work?
Only to a limited extent. Ordinary table salt is hygroscopic, but it isn’t an especially effective household desiccant. A glass of salt won’t meaningfully dry out a very humid car or fix water leaking into the cabin.
For persistent condensation, it’s better to identify the source of moisture—wet floor mats, a leaking door seal, clogged drains, or water entering through the ventilation system—and use the car’s A/C and defogger appropriately.
And if you try the salt method, keep the container stable and sealed enough to prevent spills. Salt can be corrosive to metal and electrical components.
