How can I clean the air holes?

Fill the cup with water, place your palm on it, turn it upside down, and squeeze.

When the water squirts out through the air-holes, they should be instantly cleaned! Also, you can use a blunt toothpick soaked in rubbing alcohol. Or a tooth brush dedicated solely for this purpose. Do not use sharp items (like needles) on your cup because they will do more damage than good.

You can also use Lunette Cupwipes by rolling the edges tight and and gently sticking them to the air holes and wiping them clean.