This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development is uncertain. The modern form combines 米 (rice) with 睘, but the original semantic and phonetic roles are unclear.
With 米 (rice) on the left and 睘 on the right, this kanji might relate to a type of rice cake or food, but its meaning is too uncertain for a reliable mnemonic.
For カイ, imagine a rare rice cake called a 'kai' cake: kai -> カイ, though the reading is not tied to a clear meaning.