
And I want you to know that
that is SINCERE. I do feel bad.
The Big Bang Theory Season 9, Episode 13

Not to "Sin City" but to "SINCERE city."
The Big Bang Theory Season 9, Episode 13

Did you make the apology
as SINCERE as I would have?
The Big Bang Theory Season 9, Episode 23

...and if I can figure out a way to do so
and sound SINCERE, I will.
The Big Bang Theory Season 4, Episode 9

If you're interested in making
a SINCERE effort to be a good teacher...
The Big Bang Theory Season 8, Episode 2