spending money vs cash

spending money and cash both are nouns.

Word	Noun	Adjective	Verb	Adverb
spending money	Yes	No	No	No
cash	Yes	No	Yes	No

As nouns, cash is a hypernym of spending money; that is, cash is a word with a broader meaning than spending money:

Other hypernyms of spending money include hard cash, hard currency.

spending money (noun)	cash (noun)
cash for day-to-day spending on incidental expenses	money in the form of bills or coins
	prompt payment for goods or services in currency or by check

spending money (verb)	cash (verb)
	exchange for cash