How to remoisten sweetened coconut after opening?
Here's a link from eHow that walks through how to moisten coconut flakes: 
http://www.ehow.com/how_8278347_moisten-dry-coconut-flakes.html

Although you are working with sweetened coconut that was once moist, this approach may still work.  They recommend you do the following:


Put a pan of water on the stove and bring it to a boil
Place a colander over the pan and put the coconut in the colander
Let the coconut absorb the steam for a few minutes and then pull the coconut off and pat dry it with a towel