bottle, vial, jar
罎 centers on a container for liquids or small items: a bottle, vial, or jar.
罎 combines 缶 (earthenware jar) with 曇, which likely contributes the sound. The character is a phono-semantic compound for a type of container.
The left side 缶 is a jar, and the right side 曇 looks like a cloudy sky over a sun. Imagine a jar so large it holds a cloudy sky inside—a giant bottle.
For ドン, picture a heavy jar dropping with a loud 'don' sound: don -> ドン, and the jar is so heavy it makes that deep thud.