vinegar
醯 centers on vinegar, a sour liquid used in cooking and preservation.
醯 combines 酉 (wine jar) with a phonetic element that also suggests sourness, pointing to vinegar as a fermented sour liquid.
The left side 酉 is a wine jar, and the right side has a container 皿 at the bottom. Imagine wine in a jar turning sour and becoming vinegar, poured into a dish.
For ケイ, picture a cake (ケーキ) accidentally made with vinegar instead of milk: cake -> ケイ, and the sour vinegar ruins the cake.
—