"She wiped his dry lips with water."
Translation:Ŝi viŝis liajn sekajn lipojn per akvo.
It's true that Esperanto will often use an adverb where English will use a prepositional phrase, but it doesn't quite work in this case. My gut feeling (as a "veteran Esperanto speaker") is that the reason is that "akve" is too vague. Does it mean "with water", does it mean "in water", does it mean "in a watery way"? It's best to specify (using per) that it's by means of water.