vinegar
醋 centers on vinegar, the sour liquid used in cooking and pickling.
醋 combines 酉 (wine jar, related to fermentation) with 昔, which likely contributes the sound. Together they express vinegar, a fermented sour liquid.
The left side 酉 is a wine jar, suggesting fermentation. The right side 昔 looks like stacked containers or old times. Imagine an ancient jar of wine that has turned sour over time, becoming vinegar.
For サク, picture a sack of sour vinegar: sack -> サク, and the sack holds the fermented liquid from the wine jar.