"The boss wants more coffee."
Translation:Chefen vill ha mer kaffe.
också is an adverb so it can go between the verb and its particle. It doesn't have to, we could also have said Chefen vill ha mer kaffe också. There can be a slight difference in meaning between these two versions as to what too refers to.
mer is an adjective in this case, and it needs to go next to the noun it modifies – "mer kaffe" is one sentence constituent.