Schmaltz
Etymology
From Yiddish "shmalts," in turn from German "Schmalz," meaning rendered fat — literally melted chicken or goose fat used in cooking. American English (via the music world of the 1930s) took the image of something rich, greasy, and laid on thick and applied it to overdone sentiment. The food sense still exists in Jewish cooking; the figurative "syrupy" sense is the one most people now use.
noun · /SHMAWLTS/
Excessive, gooey sentimentality, especially in music, film, or writing.
What it names
The exact word for art that lays the emotion on too thick — handy when something is not just sad or sweet but manipulatively, syrupy-ly so.
Example
The finale was good until the last five minutes, when the swelling strings tipped it into pure schmaltz.
Related idea
Kitsch is bad taste that may be knowing or ironic; schmaltz is specifically about laying on emotion too thickly.