It can get really icky especially if the person likes sweet coffee. I would suggest maybe gently telling your partner that his/her breath isn't fresh...I know I hate thinking my partners don't want to kiss me because of something as simple to take care of as icky breath.

Now if the problem persists after brushing the teeth or mouthwash a trip to the dentist, followed by a visit to your Dr. office might be in order. Gingivitis, tooth decay and sinus infection/allergies can cause halitosis that is not solved by simple tooth brushing or mouthwash.

Sugar free gum with breath fresheners is also a good bet...though the effect won't last as long as tooth brushing.