彼の話は砂を噛むようで、聞いているのが苦痛だった。
His story was so dull it was painful to listen to.
無味乾燥 is a four-character compound meaning 'dry and tasteless' or 'prosaic', often used for writing or speech; 砂を噛むよう is more vivid and colloquial.
Standard kanji spelling for this idiomatic expression.
Kana spelling of 噛む; common in casual writing.
Alternate kanji for よう; less common and may appear literary.
A set phrase literally meaning 'like chewing sand'. The exact origin is uncertain, but it is a natural metaphor for extreme dryness and lack of flavor.