Here follows a passage from Jeffery Deaver's Copycat short story:
"Relax, Wallace. Investigations take time. Sit back, take your jacket off. Enjoy our wonderful coffee." Wallace glanced at the closet that served as the police station's canteen. He rolled his eyes and the ominous tone of earlier was replaced with a laugh. "Funny. I didn't know they still made instant."
And a couple of paragraphs further:
Returning to his office, he sat back, sipping the, yeah, disgusting instant coffee, and read the file…
My question is about the "yeah" ("yes") positioned after the article and enclosed by commas.
Regarding what it means, there's no doubt whatsoever.
What this literary device is called and how it may work in the like sentences and with some words other than "yes"—should you be so kind to suggest a couple of those—is what I'm expecting to get the answer to.