A good long suck, or a quick blow...
You may have to squeeze and pump the source...
Watch out it doesn't spurt everywhere, its a bugger to clean up...
Are they in the tube or the head? and how much can you dismantle?
In the tube, just going to have to flush them out, push some ink through with a syringe if you have one.
In the heads - you can try giving then a few quick hard taps on a hard surface (print head upwards - then its down to cleaning cycles I'm afraid - not heard of any other ways :sad1: