The age old question has finally been answered: why do ice cubes crack in drinks?
Long story short, ice cubes crack because of differential expansion. This is basically saying that when the ice hits your drink, which is warmer than the ice is, the outside of the ice warms up faster than the inside of the ice.
Since the outside warms up faster, it begins to expand. This expansion happens faster than the cold inside, which causes the cubes to crack up.
Fun fact: If you leave your ice out at room temperature for several minutes, the ice will warm up on the inside, and it won’t crack when you throw it in your drink.
Check out the video below for a full explanation of the icy phenomenon.