The problem with a giant daily target is that it lives in the future until it suddenly becomes a task at eight at night. A better cue is already hiding in the shape of your day.
Drink a glass when you wake, another with lunch, one after moving your body, and one when the workday ends. These are transitions, so the action has something solid to attach to.
Make water easier to notice
Use a glass you like. Put the carafe where you work. Add citrus if the pleasure helps. Behavior that looks decorative is still behavior, and beauty is allowed to be practical.
The simplest habit is the one your day can remember on your behalf.
Needs vary with weather, food, activity, and the person. Let thirst and context matter. The routine is a prompt to pay attention, not a universal prescription.