If a person does something good or bad in this life, does god punish or reward them in their next life?

Hardeep ji, Sikhi doesn’t believe in reincarnation. There is no afterlife after our physical death.
We believe in Karma. What we sow so shall we reap. That will happen in this life,

We go into reincarnation in this life we call it a spiritual reincarnation. Our mind goes into spiritual births and deaths many times a day. We can acquire the traits of animals and act like animals. This happens when we loose divine virtues and taken over by vices

Akha jeeva visrai mar jao II Ank 9
I am alive when i live with the virtues of the creator, I die when I do not

Naam Vihuane bharnseh avah javeh neet II Ank 1087
Those who doesn’t live with the virtues reincarnate every day with falsehood
There are many shabds in SGGS on this cocept

Here is a shabd by Satguru Arjan Dev Ji explaining where we go after our physical death
Pavne mei pavan samayia jyoti mei jyot ral jaeeia II Ank 885
Maati maati hoee ek II

Air (breath) mix with air, the life force mix with Paramjot and the dead body (dust) mix with dust.
We go where we came from. Nobody has come back to tell us!