Training a baby to use a straw cup is a learned skill that requires patience and modeling. You can demonstrate the action by drinking from the straw yourself in front of them or using short online tutorials to guide the process. Weighted straw bottles are often the easiest for beginners because the weight helps keep the straw in the liquid regardless of the cup's angle. If they struggle initially, keep offering it consistently and allow them to explore; many babies figure it out through trial and error within a few weeks.