Usually, when pour water into a glass, the more thick glass is easier to burst. Because the glass tumbler is cold, When hot water is poured. The inner wall expands rapidly due to thermal expansion and contraction. But because glass is a bad conductor of heat, If the wall is thick, the temperature will not go to the wall quickly. So the inner wall expands, but the outer wall remains the same. Thus, it will cause the explosion of the glass to break.
And the thinner cup, because when poured into hot water. The heat conduction is faster, and the temperature difference between inside and outside is small. The deformation of the inner and outer walls is also small, so it is not easy to break. If slowly and small, pour the boiling water and shake the cup at the same time. If the cup is evenly heated inside and outside, it will avoid cracking.