First, find the source of the problem,then seek a dentist's advice on how to treat it well the dentist should be able to help to find the cause. Apart from improper brushing of both the teeth and tongue, bad breath could also be as a result not urinating when the bladder indicates the need and so this causes the bladder to stretch leaving residues of urine in the bladder even after one pees. Also bad breath can result when one eats a lot of spicey foods and don't floss,brush properly and gargle with an oral antiseptic wash. I could say more but first check with the dentist.

… BESIDES visiting a dentist for halitosis.. I'm talking about short term cures.. like after smoking, drinking, etc.
DR MARGARET & some others: READ THE WHOLE QUESTION BEFORE THAT "WAR & PEACE" BOOK SIZED ANSWER! you didn't tell me anything that I already knew. Christ, people.. READ THE QUESTION. .THEN UNDERSTAND IT BEFORE YOU ANSWER.

parsely of course.
mint leaves also work

My miniature Schnauzer’s breath is almost unbearable!!! He’s a great dog and as cute as can be but his breath is horrible. Any suggestions on how to safely cure his halitosis?
Tartar build up is very common in small breeds. They are also prone to having bad teeth and gingivitis. I have two poms and take them in regularly to get their teeth cleaned approximately every 2 years. I would strongly suggest to have your dogs teeth cleaned. It makes a world of difference! http://www.animalcliniccalgary.com/images/IMG_1128.JPG