Apple cider vinegar is certainly a metabolism-boosting food, as is green tea, celery, cinnamon, chilli, ginger and water. Remember though, that none of these foods are a miracle metabolism-booster, and will not have any significant effect if not coupled with regular exercise and clean eating. HIIT training, and strength training in particular will boost your metabolism, as they keep it fired up long after the exercise session is over. Remember to eat smaller more frequent meals during the day, always starting with an energy and protein packed breakfast, as well as water as soon as you wake up.