Drink water in between meals, not with meals. If you drink fluids with meals, you increase the volume of stomach contents, which makes it easier for heartburn to happen. You can also try these stomach-cooling juices for heartburn relief: papaya, mango, guava, pear. Or run a cabbage or raw potatoes through a juicer for a natural drink to soothe stomach burn.
Buttermilk is also an acid-reliever, but don't confuse it with regular milk, which can be an acid-maker, especially if you are bothered by lactose intolerance.