Keto breath 🤢

My bf has been keto since last year I don’t know the date I just know he started keto in the spring so it’s been almost a year. He has horrible breath! And I know it’s normal during the adaptation period but I bring it up to him, he will brush his teeth and it still stinks. I’m thinking it’s dehydration. He was drinking coffee all day at work and not really much else and he fasts and eats OMAD everyday He switched to herbal tea today to see if it helps. He brushed his teeth this morning but he just got home and his breath reeks! I mean it’s so bad I smell it standing a foot away from Him. I feel so bad I keep bringing it up because it can hurt someone’s self esteem but it’s unbearable