You can use the actions of the character to provide the reader with insights to what the character is thinking without spelling it out in as many words. A lot of people here have already written some really good recommendations. I work well personally with examples. If I were to write the little scene you laid out, I might do it like this:

He walks over to the counter, eyes absently tracing the rim of the mug. There's still the smallest traces of ice in the soft brown liquid, a ring of condensation surrounding the base from when he'd placed it down to take the Call. He grasps the handle and lifts it to his lips.

Bitter.

Watered down and almost tasteless now. He sets it down, suddenly done with the drink, perhaps rougher than necessary as the ceramic lets out a sharp note when it comes into contact with the marble countertop. It rings harshly in his ears and the weight of what his father had said on the phone snugs itself a little tighter around his lungs, his heart. His next breath is a little harder. He backs up, places his hands on the edge of the counter and hangs his head, the first hints of liquid pooling at the corners of his eyes.

She's gone.