I don't do the day hike thingy any more but when I did...
2 liters to Trailside Meadow.
Have a meal and go to 4 liters...just one stop.
Check water at the seeps on switchbacks on the way down...if I need water add it here.
Stop at Trailside Meadow for sustenance, head dunk and foot soak.
Then back to Whitney Portal for a shower and Chicken Sandwich and Fries.
It's a real simple plan.