Hi, 6 months is an age which brings lots of questions to mothers and lot of new challenges. Giving water to your little one is of your choice. There is no specific number but you can give him after each meal.Water can be given between meals.Your baby would any day prefer milk over water so the quantity that he would take wouldn't be much anyway.The only thing you need to keep a track is about adequate weight gain and adequate number of times of passing urine,especial with the summer approaching. Happy parenting !!