。
I'm out of energy.
Literal
I [topic-は] energy [object-を] use-up-ran-out.
使い果たす is a vivid compound verb: 使う ('to use') + 果たす ('to complete, exhaust'). The 果たす element means 'finish completely / achieve to the end,' so the compound means 'to use up completely, to exhaust.' Common in expressing depletion of resources, energy, patience, money.