Final answer:
The nurse should document the client's oral intake of water as 120 mL of fluid on the intake and output record, as it pertains to fluid intake.
Step-by-step explanation:
When calculating a client's fluid intake over the past 8 hours, the nurse should plan to document the client's oral intake of water as 120 mL of fluid on the intake and output record. The options provided include administered IV antibiotics (which would typically be considered part of fluid intake), emesis, and urine output, which are related to fluid loss rather than intake. Considering the context of the question, the water that the client drinks is the type of fluid intake that should be documented as part of the client's fluid balance.