Permanent markers don't run out of ink. Rather, they dry out over time. You can revive a dried-out marker with a common household ingredient.

When we think a permanent marker has run out of ink, what has really happened is that the solvent from the ink-solvent mixture has evaporated from the wick, and the ink no longer flows to the tip of the marker.

To wet the marker again and allow the ink to flow, inject the wick with nail polish remover using a hypodermic needle. Nail polish remover is the same type of solvent that the wick originally contained.

You may use the acetone-based nail polish remover, or the acetone-free kind which works just as well and stinks less.

You can test for ink/solvent compatibility by placing a teardrop-sized drop of solvent on the tip of your marker - if it writes after you place the drop of solvent on the tip, it is compatible.