Dr my friend is 18 weeks preg, last scan we came to know fluid is low, doc advised to drink more water and milk, it will help to increase the fluid?

Maybe : It depends on why the amniotic fluid volume is low whether or not increased fluid intake will help. If it is due to a fetal anomaly it may not make a difference but it definitely won't do any harm. You may need referral to a specialist in maternal fetal medicine, a subspecialty of OB/GYN to guide you if the fluid is extremely low or doesn't improve by the next ultrasound. Hope this helps.