replaced the battery with a new one as well as the alternator and still won’t hold a charge
That is a very wide open statement. This could mean so many things but I’ll make a wild donkey guess. You have some electrical device with a small internal short draining the battery overnight. Likely an aftermarket radio, amplifier or sub-woofer. Other contenders for this are aftermarket alarms or remote starter. If you have any of these, disconnect them or pull their fuses. See if the drain goes away. If the easy fix doesn’t work, have your mechanic do a parasitic drain test.
Good battery. Check
Alternator is putting out 13+v at idle? Check
Quick and dirty. Install battery disconnect.
Find hidden current draw.
Have you checked your battery connections . . . ?!
Unless you remove the battery bolts from the cable and inspect them, along with the cable, you can’t cross them off your list
it’s NOT enough to just remove them from the battery
To literally get the full picture, you have to separate the bolt from the cable, remove the rubber sheath, and inspect everything