A powerful vaccuum if you have one.

Or take the cage outside and use a hose with a reasonable pressure nozzle on it.

You can buy canned air at radio shack for pretty cheap. It is a can of pressurized air with a nozzle and a straw to focus the air blast. Primarily used for blowing dust off of circuits, debris out of keyboards, etc. Point at the track and shoot. Wear eye cover if there is sand being blown out.

I hope that helps.