How to rejuvenate water-based markers

I don't play with markers much. My childhood experience with them was not particularly positive. I love the intense colours achieved, but the markers dried out fast or their nibs got soft and splayed quickly. 

I recently acquired a bunch of old markers for charity and wondered how to revive them. 

The internet says to soak in water. 

I tried putting drops of water on the tip. The marker tips soaked up the water hungrily, but it diluted the ink. With FaberCastell connector pens, this technique diluted the tip so much they couldn't write anymore. I thought I had ruined the markers!

In the end, I tried dropping fountain pen ink, drop by drop onto the marker nib. That worked wonderfully. Again, the tips soaked up the fountain ink hungrily. When used, the resulting colour is bright and intense. No dilution. The markers felt heavier after I was done, so they must have gained something. 

I was tempted to use a small needle and syringe like this girl:

I will try diluting the fountain pen ink to get more mileage for each marker.