ગધેડાને સાકર ઝેર.

gadhēḍānē sākara jhēra.

Literally: Sugar is poison to a donkey.
What it means: Good advice, fine things, or kind treatment are wasted on, or even rejected by, foolish and unappreciative people.

Also said as

ગુજરાતી કહેવતસંગ્રહ (Gujarati Kahevat Sangrah) (1923) ગુજરાતી કહેવતસંગ્રહ (Gujarati Kahevat Sangrah) (1921) · read from the scan by machine — the Gujarati itself is unchecked · English is machine-made and nobody has checked it yet

Heard it differently, or know we've got the sense wrong? Tell us — that is exactly the kind of correction this needs.