As proper supported diaphragm breathing pushes the diaphragm (and also esophagus) downward, the stomach acid will flow into the esophagus and irritate acid reflux.
1. Don’t eat before singing.
2. Don’t drink carbonated drinks with caffeine (most carbonated drinks have caffeine).
3. Don’t drink caffeine.
If must sing, then use an antiacid. These usually last 30 to 60 minutes, so will be very useful for singing and diaphragm breathing while with food in stomach.
Singing and posture--see Categories, About, Launch 4-2014 