How do I dry out my double walled travel mug?

I have a double walled travel coffee mug that I like but it seems moisture keeps collecting between the metal inner mug and the clear plastic outer lining. I have tried leaving it in the sun both flipped up and flipped down and cant seem to get it out. In the past it has gone away, but this time I cant get it out.

I have seen suggestions like drilling a hole which I would like to avoid. Is there a way to disassemble this to dry it out ? Or some other way?

Many thanks.