What is the equivalent of a "W" sound in Japanese and Chinese ?

 There are no single consonants equivalent of Latin alphabet in Chinese and Japanese.

In Chinese and Japanese, Latin alphabet consonants always following by vocal aiueo. So Chinese and Japanese made some adaptation pronunciations following by vocal alphabets, so no fixed pronunciation for W in English. Example like…

Wa is like

华 Hua in Chinese,

ワ Wa in Japanese.

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Wi is like

威 Wei in Chinese,

ウィ Ui in Japanese.

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Wu rarely seen in English but often seen in Chinese. It's like

五 Wu in Chinese,

ウ U in Japanese.

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We

We have similar pronunciation with Wi in Chinese and Japanese at previously mentioned.

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Wo is like

我 Wo in Chinese,

ヲor ウオ in Japanese.

Ellen Baker, character from Japanese-English Book New Horizon.