unstrained spirits
醅 centers on unrefined, cloudy alcoholic liquid: specifically unstrained spirits or raw sake lees. The idea is a drink that has not been filtered clear.
醅 combines 酉 (sake jar, alcohol) with 咅, which likely contributes the sound and may relate to the idea of something unseparated or still in process. The exact historical development of 咅 in this character is uncertain.
The sake jar 酉 on the left holds a cloudy liquid, and the right side 咅 looks like a stopper or something still mixed in. Picture a jar of unstrained spirits, thick and unfiltered.
For ハイ, imagine a tall glass of hazy, unstrained spirits and someone saying 'Hi!' to the cloudy drink: Hi -> ハイ.