I've spent a fair share of my life having rented living spaces, and this is how I dealt with smelly refrigerators of units I rented.
#1 Empty refrigerator completely, pull refrigerator out into the room, unplug. Often times you'll find a previous spill has left a nasty something underneath. Clean the floor under the entire refrigerator "zone".
#2 locate condensor/coils and drip pan, remove drip pan and wash in warm water, dry completely, set aside. Vacuum dust from coils. Investigate drain tube that leads to drip pan (a q-tip works nicely) determine if there is "gunk" or growth in the tube.
#3 Remove all drawers/trays, shelves and accessories in the freezer compartment and refrigerator, wash, dry and set aside.
#4 Check the door side of the freezer compartment floor and look for venting holes, investigate for food materials (spillage) and clean up if found; locate drain at base of refrigerator compartment (often is under the drawers when installed) clean up.
#5 Investigate the door compartments (often times location of hidden spills that have dried found on underside of door 'shelves').
#7 Clean the folds and the faces of the gasket seals for both the freezer door and the refrigerator door, paying special attention to the underside of both freezer and refrigerator doors.
#8 Since you have already used baking soda and water to clean I suggest my old standby of Scrubbing Bubbles in the can (bathroom sink cleaner). With a brand new sponge, a bucket of clear water, spray on surfaces, then wipe off with rinsed and squeezed out sponge. After cleaning all surfaces and rinsing, with fresh water and fresh sponge, repeat rinse process a second time changing water frequently.
#9 prop both the freezer door and refrigerator doors open, and allow to remain open without power overnight, airing it out and drying completely.
#10 Back the refrigerator back into position and plug in.
#11 Prop both the freezer and refrigerator doors open, and allow the refrigerator to run for 15 minutes with the doors open to allow for a complete air exchange.
#12 Temporarily re-install two shelves in the refrigerator one at the highest point possible, and one at the lowest point.
#13 Take 2 or three freezer safe bowls and fill each with 1 fresh box each of Baking Soda, place one in the center of the freezer and two in the refrigerator (one on top shelf, one on lowest shelf in the center of the refrigerator shelf area), and close both freezer and refrigerator doors. Return to the refrigerator every 2 hours and STIR the baking soda. After 8-12 hours, remove the bowls, throw AWAY the STINKY baking soda (you might not notice an odor esp. as its cold, but throw it away), wash and dry the bowls, and re-fill with NEW fresh baking soda and replace in the refrigerator, leave in place another 12-24 hours. Dispose of this baking soda as well afterwards, replace all drawers, shelves, accessories in the refrigerator and freezer compartments, install three new fresh bowls of baking soda in the aforementioned locations, and put your food in the refrigerator. this should elimate the old odors and control new potential odors. Be sure to replace the baking soda on a regular basis as the need arises.
It may take a few weeks as the heated air (yep frost free freezers use heated air to remove moisture from the air in the freezer compartment, that's how it prevents frost build-up) cycles and the air exchanges thru both compartments, but that should take care of the problem.
good luck, hope this helps. By the way that scrubbing bubbles is fantastic for restoring vinyl/pvc mini-blinds as well, you take them down, clean in the tub, rinse, let them dry, and look like new, even cleans the roping if stained by tobacco smoking, quite nicely.