I know this is obvious but sometimes I need a little reminder - drinking enough water makes me feel good. I drink lots of water because I'm currently nursing Baby Boy and also - I just like water!
When we were driving to Lewis we had a day where we drank more soda that we should have. The next day we had no soda but plenty of water. Although I didn't feel bad the first evening, on the second (water day) evening, I felt great.