I’m thinking of a paperback of solve-yourself type mysteries, 1970s or 80s. There was one short story where the solution involved a hot dog with sauerkraut, and the big “Clue” was supposed to be that the perpetrator had put the mustard on top of the sauerkraut instead of underneath it. It baffled me as a child, it baffles me today.
Solved! “Encyclopedia Brown The Case of the Hidden Penny” solved by Ross and an anonymous Lost Classics reader!
Lost Classics of Teen Lit: Name That Book! 
I think this is an Encyclopedia Brown mystery??
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This was an Encyclopedia Brown. Buzz Meaney hides a stolen rare coin in a hot dog. Encyclopedia figures it out because it is utterly inconceivable that anyone would put mustard ON TOP of the saurkraut.
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Oh, forgot the citation: https://www.tumblr.com/brownencyclopedia/26636465912/the-case-of-the-hidden-penny
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This is definitely correct! It’s funny, I read this one as child and was thinking about it the last time I went to get a hot dog with sauerkrat and mustard, applied in the proper order. Thank you, commenters, I am markingthis as solved!
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