It is important to eat as healthy as you can. In a recent study, ex-smokers who had the highest fruit and vegetable intake had the best quit rates (2-3 times higher). There are probably multiple factors involved. Fruits and vegetables, non-caffeinated beverages, and dairy products may worsen the perceived taste of cigarettes. The fiber, water content and nutrients in fruits and veggies may relieve hunger pains and help maintain bowel function and weight after quitting. They may also influence the dopamine levels in the brain to lessen cravings for cigarettes and anxiety/depression from withdrawal. Always be sure to drink lots of water and eat plenty of whole grains.
J. P. Haibach, G. G. Homish, G. A. Giovino. A Longitudinal Evaluation of Fruit and Vegetable Consumption and Cigarette Smoking. Nicotine & Tobacco Research, 2012; DOI: 10.1093/ntr/nts130