Is there anything more pathetic than trying to draw with a dried up marker? Not according to my three children. And yet interestingly enough that hasn't made any of them (ages 2, 2, and 4) more likely to put the caps on their markers when they're finished with them.
Quite by mistake I discovered a use for these nearly dried up markers that we seem to have in abundance. My favorite part about food coloring was always watching the colorful clouds disperse in the water, so one day I decided to see if I could get the same effect with a marker in my children's water table. Turns out there is a surprising amount of color left in those markers that seem to be nearly dried up. We now use them for fun in the water table, the water-filled sink, or in a clear cups of water.
This is also good for color mixing lessons, which for us really consist of the same amazement that mixing every color together always creates brown.