exhaust, run out, use up, empty
罄 centers on complete depletion: using something up until nothing remains, leaving an empty state.
罄 combines 殸 (a phonetic component with the sound ケイ) and 缶 (a jar or vessel), suggesting a vessel emptied to the last drop.
The top 殸 looks like a tool striking something, and the bottom 缶 is a jar. Picture striking a jar upside down until every last bit is exhausted and it's completely empty.
For ケイ, imagine a cake jar that's been scraped completely empty: cake -> ケイ, and the jar is exhausted.