Improvement of Functional Dyspepsia After Drinking Alkaline Ionized Water From Alkaline Ionizer

The goal of this clinical trial is to evaluate the effect of drinking electrolyzed alkaline reduced water (EARW) compared to drinking purified water (PW) on functional dyspepsia (FD) patients. The main question\[s\] it aims to answer are: * Drinking EARW (EARW group) will alleviate gastrointestinal (GI) symptoms and FD symptoms compared to drinking PW (PW group). * Drinking EARW will make higher the FD-related Quality of Life (FD-QOL) compared to drinking PW. Patients will drink EARW 10mL/kg/day body weight for 6 weeks according to the instruction of researcher using the experimental device installed at each patient's house. After 6 week, EARW and PW groups will be compared to evaluate effect of GI symptom and FD-related QOL.