I bought quite a few cabinets that were store returns. Quite a few had either came apart or needed some pieces replaced. Most of the repairs I did was replacing sides because the hinge screws blew out of the plywood or re-gluing the cabinet door.
Since the cabinets were white, I bought some white shelving from menards that were a little thicker. I then cut pieces to fit and re-attached the sides.
Several of the front doors weren't glued very well and fell apart, so I made a holding jig that would allow me to clamp the sides together while the glue cured.
Two of these cabinets were deemed good enough to become the medicine cabinets in the master bath, which I will call a success.