Unless there's the word jokin (jotain in partitive), meaning 'something/some', the word 'some' is optional.
The English word 'some', when immediately preceding an uncountable mass noun, means "an unspecified amount", to quote Wiktionary.
A mass noun is by default an unspecified amount, so 'some' doesn't really add more information to the sentence. "Does he want coffee?" and "Does he want some coffee?" are both valid translations of 'Haluaako hän kahvia?'