drought, dry, dessicate, drink up, heaven, emperor
乹 centers on dryness and lack of moisture: drought, desiccation, and drinking something up. The extended senses of heaven and emperor are likely borrowed from the related character 乾 and do not grow naturally from the dryness idea.
乹 is a variant or simplified form of 乾. The character 乾 combines 倝 (a phonetic component associated with dryness) with 乙, but the exact historical development of the simplified 乹 shape is uncertain.
The left side looks like a dry, cracked surface under the sun 日, and the right hook 乚 is like a last drop of moisture curling away. Together they show extreme dryness.
For カン, imagine a dry, empty can baking under the sun: can -> カン, and the drought has left everything parched.