Oversweet (5)
(Other definitions for sappy that I've seen before include "Full of juice" , "Succulent" .)
'oversweet' is the definition.
(thesaurus)
This is all the clue.
(Other definitions for cloying that I've seen before include "Sickly sweet" , "Overly sweet, saccharine" , "Sickeningly sweet" , "Nauseating" .)