Question: If "reek" is used as a term to describe something that smells bad, what word of equivalent meaning would describe something that tastes bad?

Answer: 
You're probably used to this in a different sense, but [disgusting](http://www.dictionary.com/browse/disgusting) means

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> causing disgust; offensive to the physical, moral, or aesthetic taste.
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The etymology of [disgust](http://www.etymonline.com/index.php?term=disgust) is "dis + taste"; in other words, it tastes so bad that feels repugnace toward it. 

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> 1590s, from Middle French desgoust "strong dislike, repugnance," literally "distaste" (16c., Modern French dégoût), from desgouster "have a distaste for," from des- "opposite of" (see dis-) + gouster "taste," from Latin gustare "to taste" (see gusto).
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**gag**

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> to experience the sudden uncomfortable feeling of tightness in the
>  throat and stomach that makes you feel like you are going to vomit
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[Cambridge](http://dictionary.cambridge.org/dictionary/english/gag?a=british)