That's the ticket or That's the ticket for soup. That's the right thing. The ticket to be shown in order to obtain something. Some think that the word “ticket” in this phrase is a corruption of etiquette.
“ `Well,' said Bob Cross, `what's the ticket, youngster? Are you to go aboard with us?” —Captain Murryat.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894
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