This is a common problem. Firstly..please increase the number of times you consume water...the best way is sipping on water every half an hour so that your mouth stays hydrated. This will solve 80 percent of the problem. Also..you can use mouthwashes like colgate plax to further reduce bad odour after you eat something.
Next Steps
If the problem still doesnt get solved..you can probably go for a routine clening/scaling to a dentist
Health Tips
SIP ON TO WATER EVERY HALF AN HOUR TO KEEP YOUR MOUTH HYDRATED.