Try to eat 30 minutes before you start your exercise, also dehydration is one of the most common causes of feeling nauseous after exercising. To keep from becoming dehydrated, you should try to drink a minimum of two cups of water roughly two hours before you start your exercise routine. 20 minutes before you begin your routine, you should drink 2 more cups of water. While you are exercising, you should also keep a water bottle nearby. During exercise, you should drink around half a cup of water for every ten to fifteen minutes of your exercise routine. If you follow these guidelines, you should be able to avoid becoming dehydrated, and to avoid the nausea that comes with dehydration. read more..