What do you call the words obtained by inversing the order of the sounds?

It is an example of Phonetic Reversal.
(or is it Phonemic reversal?, as Jon Purdy points out in the comments: reversal of the order of the phonemes /ch/, /ea/, and /t/ rather than the phones [t], [ʃ], [iː], and [t] or [ʔ]).

It could be an instance of backmasking, even though the Wikipedia article does mention:

Phonetic reversal is not entirely identical to backmasking, which is specifically the reversal of recorded sound.
This is because pronunciation in speech causes a reversed diphthong to sound different in either direction (e.g. eye [aɪ] becoming yah [jɑː]), or differently emphasize a consonant depending on where it lies in a word, hence creating an imperfect reversal.

Backmasking involves not only the reversal of the order of phonemes, but the reversal of the phonemes themselves, which means that the reversed sound of a phrase may be hard to predict.

So I am not sure that the word "teach" played reversed would actually gives "cheat".
If it doesn't, I didn't find any "one word" to characterize this particular inversion.