焼け石に水
や
け
い
し
に
み
ず
Meanings
1
a drop in the bucket; too little, too late; futile effort
Idiomatic expression meaning that a small effort or amount is completely inadequate to solve a large problem, like pouring water on a hot stone.
A donation this small is just a drop in the bucket.
Cleaning alone is a futile effort; it gets messy again right away.