It'd be more likely to find approval if it were each adventurer having a chance of having a single empty keg filled.
I dont understand why you find this to be too powerful.
What your proposing is way to underpowered.
I agree with Zakky, i wouldnt care for a scroll that 'could' refill only one keg.
If Beer was endless, i agree the whole resting part of the advy game would become useless.
But its easy to fine tune its effects.
and besides, as Zakky stated, scrolls are very rare.