One. Caulking repair with glass glue
For situations where a toilet bowl cracks, if the cracks are small, clean them thoroughly. Then, you can apply ready-mixed putty paste directly to the cracks. It's best to apply it evenly on both sides. Use a hair dryer to speed up the drying process. After 24 hours, check the results. If it doesn't work, try applying it again.

II. Replacing the new toilet
However, if the cracks in the toilet are too severe, it is best to replace it for peace of mind. Moreover, using putty paste is not a long-term solution, and it will eventually continue to crack over time.
Three. important considerations when replacing a toilet.
First, the waterproofing for the toilet should be completely redone to ensure no leaks, as this can cause problems for the apartment below.
Second, pay attention to the dimensions of the toilet, which must be the same as before. Otherwise, it will be difficult to install.
Third, it is best to remove the tiles around the toilet as well, as this will also prevent adhesion issues.