Question

plz answer why does water stick to a cold surface on a hot moist day

Answer 1

There is moisture in the air, this is often called "humidity". The amount of moisture that can be in the air depends on the temperature of the air. The warmer the air is, the more water it can hold in it. When the air comes up against the cold outside of a cold bottle, the air right next to the bottle gets cold. It gets so cold that it can't hold as much water anymore and some of the water "condenses" or comes out of the air onto the bottle. That cold air next to the bottle is heavier than the air around it (hot air rises, cold air sinks) so the colder air with some water out of it sinks, and fresh water filled air comes in to get cooled and leave some more condensation. 

This process is similar to what causes clouds to form and rain to fall. 

Answer 2

This is because as the moisture outside the glass comes in contact with the cold surface of glass, it condenses to form water droplets which are seen as water drops sticking to the outside of the glass.
Hope it helps :)