  We thoroughly investigate the effect of nonmagnetic Sn doping on the
electronic and magnetic properties of antiferromagnetic topological insulator
MnBi$_2$Te$_4$. We observe that Sn doping reduces the out-of-plane
antiferromagnetic (AFM) interactions in MnBi$_2$Te$_4$ up to 68\% of Sn
concentration and above the system is found to be paramagnetic. In this way,
the anomalous Hall effect observed at a very high field of 7.8 T in
MnBi$_2$Te$_4$ is reduced to 2 T with 68\% of Sn doping. Electrical transport
measurements suggest that all compositions are metallic in nature, while the
low-temperature resistivity is sensitive to the AFM ordering and to the
doping-induced disorder. Hall effect study demonstrates that Sn actually dopes
electrons into the system, thus, enhancing the electron carrier density almost
by two orders at 68\% of Sn. In contrast, SnBi$_2$Te$_4$ is found to be a
p-type system. Angle-resolved photoemission spectroscopy (ARPES) studies show
that the topological properties are intact at least up to 55\% of Sn as the
Dirac surface states are present in the valance band, but in SnBi$_2$Te$_4$ we
are unable to detect the topological states due to heavy hole doping. Overall,
Sn doping significantly affects the electronic and magnetic properties of
MnBi$_2$Te$_4$.
