Question

WHEN YOU DRINK THROUGH A STRAW WHAT FORCES THE LIQUID UPWARDS ?

Answer 1

when we drink through a straw then the atmospheric pressure forces the liquid upwards. when we suck through the straw, the pressure decreases in that area and the liquid moves towards that. 

Answer 2

When you drink from a straw, you create a little space of low pressure inside your mouth and in the top of the straw. Then the air outside the straw pushes down on the surface of the drink and forces the liquid up through the straw and into your mouth.