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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Not sure that there is a comparable word as 'taste' by itself (even in context) does not have an alternate meaning that implies unpleasantness. 'Smell' can imply unpleasantness.

Example:

"Something smells."
"Somethings tastes."

..and as an adjective can in fact imply pleasantness...

"That is smelly."
"That is tasty."