Most guys need to hear things straight up. Beating around the bush to get a point across does not work well with most guys.
Ask him what he has been eating and when was the last time he brushed his teeth. Let him know that your not trying to be mean, it's just that his breath has become unbearable and he needs to consider taking some additional steps to help with it.
I also suffered with bad breath when I was younger and wish that people had told me so that I can do as I do now and use mouthwash several times a day. I also found that different types of foods and drink can cause it. Milk, onion, garlic, potato, candies, soda, the list goes on and on.
Make sure you are on your own, ask him a few questions about if he has had a cold recently, has he had or does he have nasal congestion, trouble breathing when asleep etc, if he does then you can drop it into the coversation that it is affecting his breath as well - he may even know this already. If he has none of these he will then ask you why you are asking - so tell him, but in a gentle way like "well your breath sometimes smells a little and I was wondering if any of those could be the cause" rather than "because your breath stinks". He might take the initiative than and do something about it.
Ask him questions like, "what did you have for breakfast/lunch/dinner today?" "How often do you brush, I brush mine _____ a day?" Turn it into a conversation and then just say it in a way that makes you feel comfortable!
Hemm in that issue ,, just tell him frankly , he is your bf better to tell him as earlier,,don't let other tell him ,, .for sure he will not be hurt that way .. No matter what happen , you just tell him the truth .. That is for him ,,
There could be a medical or dental related condition for his bad breath. I liked the suggestion of the other lister. If that isn't something you feel comfortable with accompany him to his dental recare appointment. If possible let the hygienist know of your concerns. She will be able to let you know if his malodor is from an infection in his 'gums', coating on his tongue or other dental related issue. If not, then look into medical reasons. Diabetes is sometimes the cause of bad breath.
It may be that he isn't brushing/scraping his tongue. About 80% of the bacteria found in a mouth is laying on the tongue.
Tongue scrappers can be purchased at the local pharmacy. Tango is one brand that can be sterilized in the dish washer. There are also plastic disposable scrappers from BreathX. Best wishes hope this helped.
You should tell him,he will be glad,he will be embarrassed a little for while,just change the subject quickly,He will happy because no ones gona tell him. And remember not to make fun of him.I Have this kind of situation before,a friend of mine have a really bad Breath,so I told her she was glad that I was the one who told her.I recommended her a breath spray called Binaca,which is very easy to carry around,they got great flavours,its Sugar free and taste really good.Gives you long lasting Fresh Breath. :)