drink may come out unevenly, with pauses, glugs, or sudden spurts.
The vent gives air another path into the cup, helping the coffee flow more consistently.
Think about pouring liquid from a bottle with a narrow neck. If air cannot move back inside easily, the liquid may come out in irregular bursts. Allowing air to enter through a separate opening can make the flow smoother.
The same basic principle applies to many takeaway cup designs, although the exact effect depends on the lid’s shape and the size and position of
