Since this word consists of a kanji with hiragana attached, you can bet that it will use the kun'yomi reading. You didn't learn that reading with this kanji, so here's a mnemonic to help you:
If you are going to go astray, one way to do it would be to eat wayyyy too much mayo (まよ). I can't think of a worse way to go astray, personally.
I’m not sure if I should buy unsweetened coffee.