盞搞 [盏－]

Jyutping zaan2 gaau2
Pinyin zhǎn gǎo

Definitions (CC-CANTO)
  1. (verb) to do something or work for almost nil; to do something but all to no avail;
Definitions (粵典–words.hk)
  1. 形容詞
    做​嚟​都​無意義​，​只​係​白​做
    a waste of time and effort
  2. 參看
    盞攪、賺搞