cup, glass, tumbler
桮 centers on a container for drinking: a cup, glass, or tumbler. The meanings are all vessels for holding liquid.
桮 combines 木 (tree, wood) with 否, which likely contributes the sound. The character originally referred to a wooden drinking vessel.
The tree 木 on the left suggests a wooden object, and the right side 否 looks like a container with a lid. Imagine a wooden cup with a cover: 桮 is a cup or tumbler.
For ハイ, picture raising a wooden cup high in a toast: high -> ハイ, and the cup is lifted up.