sugar apple vs custard apple

sugar apple and custard apple both are nouns.

Word	Noun	Adjective	Verb	Adverb
sugar apple	Yes	No	No	No
custard apple	Yes	No	No	No

As nouns, custard apple is a hypernym of sugar apple; that is, custard apple is a word with a broader meaning than sugar apple:

sugar apple: sweet pulpy tropical fruit with thick scaly rind and shiny black seeds
custard apple: the fruit of any of several tropical American trees of the genus Annona having soft edible pulp

sugar apple (noun)	custard apple (noun)
sweet pulpy tropical fruit with thick scaly rind and shiny black seeds	the fruit of any of several tropical American trees of the genus Annona having soft edible pulp
	any of several tropical American trees bearing fruit with soft edible pulp