"with" here means "contains" or "have"
"with cream" in "coffee with cream" is an adjectival phrase that describe the noun coffee.
I drink coffee
the coffee that's with cream
I always drink coffee = 我总是喝咖啡
I always drink coffee (with cream) = 我一向喝(加了奶油的)咖啡 or 我一向喝(有奶油的)咖啡
If you are having a cup of black coffee and a cup of cream at the same time, then 'with' would mean "together" and coffee and cream would be of equal weight. That is not what the sentence in your question meant. in "I always drink coffee with cream", coffee is the main object, cream is an addition
More example of "with" meaning "contains" or "have"
"book with pictures" (book that contains pictures)
"people with money" ( people who have money)