Question

Why do more ice cubes make a drink have a lower temperature

Answer 1

Because ice floats, it cools the water near the top of the glass first. As the top layer of water cools, its density increases, causing it to sink to the bottom. The lower layer, less dense and therefore more buoyant, floats to the top and is cooled in turn.

Answer 2

We know that heat is transferred to its surroundings to maintain thermal equillibrium .So here the drink is trying to keep thermal equilibrium with the ice cubes so as a result ice and the drink transfer their temperatures to each other making the ice melt and making the drink cool 
THIS PROPERTY IS KNOWN AS THERMAL EQUILIBRIUM
HOPE THIS HELPS 
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