meal vs sustenance

meal and sustenance both are nouns.

Word	Noun	Adjective	Verb	Adverb
meal	Yes	No	No	No
sustenance	Yes	No	No	No

As nouns, sustenance is a hypernym of meal; that is, sustenance is a word with a broader meaning than meal:

Other hypernyms of meal include aliment, alimentation, nourishment, nutriment, nutrition, victuals.

meal (noun)	sustenance (noun)
the food served and eaten at one time	the act of sustaining life by food or providing a means of subsistence
coarsely ground foodstuff; especially seeds of various cereal grasses or pulse	a source of materials to nourish the body
any of the occasions for eating food that occur by custom or habit at more or less fixed times	the financial means whereby one lives