Many objects fill our pockets every day but are they really useful on a hill/mountaintop?
Assuming that you usually reach the location by private car for a one-day excursion, these things do not need to take a walk with you:
home keys: just store in a pocket your car keys (better in a pocket that will not be opened until you need your car keys again)
complete wallet, it may even stay at home: carry your driving license, an ID document, few banknotes and debit/credit card
coins: leave them in the car
sun lotion: carry an almost-empty tube, or get hold of some samples
glass bottles/containers: plastic is lighter than glass