Puffy fruit in tomato is caused by

Puffy fruit in tomatoes is caused by a Physiological disorder.
Tomato puffiness is slab-sided fruit with hollow gaps between the outer wall and locules and a reduced number of seeds. It is caused by extreme environmental conditions such as high or low temperature.
Puffiness results from incomplete pollination, fertilization, or seed development often as a result of cool temperatures that negatively impact fertilization.