They've been working for hours, more or less in shifts. Jake's been at it longer than Barnes has, he's only just begun to sweat and he's still got hours left in him probably. He's pausing to grab a drink when Jake corners him with the request, and it gets eyebrows shooting up to his hairline.

"Borrow... my energy," he repeats in a sort of flat echo, just to make sure he heard that right. What the hell does that even mean? Jake's holding out a hand like he means it literally, and... What?