When hanging cabinets from the ceiling that are not against a wall, then some good backing has to be installed in the ceiling framing. If the ceiling can be accessed from the attic then do so from there, but if you have a vaulted ceiling then tear up some dry wall to get to the framing.

Nail flat 2x4's or 2x6's between the rafters above the drywall along where the cabinets will go. patch and texture the drywall.

Hang the cabinets using a cabinet stand to hold them up while screwing in small lags with washers, or strong screws with washers, strait up into the framing.

Cabinets were not designed to be installed this way, but there is no other choice unless you want to get fancy with some kind of metal brackets. It is not a bad idea to supplement the top of the cabinet with extra plywood before screwing them in.