what to do if my almost 6 month old baby doesn't want to drink milk

My almost 6 month old doesn't want to drink milk. I've tried changing his bottles' nipples, fed using syringe, medicine dropper but still refuses to drink milk. I brought him for a check up and hia pedia said that he's not teething yet, and it's normal for babies to lose interest in milk but I still have to try and make him drink his milk .. But HOW??? Can someone help me