Off and on I've noticed a smell emitting in my kitchen area, primarily from the dishwasher, which I don't use. Other times it comes from the garbage disposal as well, but it doesn't seem to be as strong there.

Lately it's been rather obnoxious, and hard to avoid. I don't know how to describe the smell, like rotten cabbage perhaps.

I've tried putting vinegar and baking soda in the dishwasher, also laundry detergent and ice in the garbage disposal; but the smell comes back.

I live in the second floor of an apartment complex. I will call on maintenance soon, but would like to know if this is sewer gas or something I am contributing to.

I am not sure what sewer gas is.

It could be from your garbage disposal.
Wedged lemons actually work quite well to remove odor from them. Give that a try and then call your maintenance person.

I hope the other pros jump on this and give you a good answer. I just had a friend describe the same problem to me( his plumbing was all to code and less than one year old) I suggested pouring a mixture of bleach and water downt the sink.
Now this could be a lot of things. Is your sink properly trapped and vented. I assume it is, other wise you would be smelling sewer gas instead of rotten food. If you don't use your dishwasher at all, disconnect the dishwasher drain from the garbage disposal and plug the disposal drain inlet. Also try filling both sink compartments with hot hot hot water and let them drain at the same time while running your garbage disposal. Please let me know if any of these things help.
If your dishwasher isn't used you may be getting overflow from your sink into your dw if the drain for the dw isn't run up to the highest point under your cabinet before connecting to your garbage disposal. Hope this all makes sense.

I haven't yet any understanding of plumbing. However the last time I ran the dishwasher I did observe that water and some food were rising up from the garbage disposal momentarily.
I can also say that I had maintenance replace the gun on the sink recently.

I doubt it is rotten food since it periodically comes back smelling the same, but who knows. I will try some of these methods.

Okay. If you have water coming up into your sink while the dishwasher is draining, you may have a partially plugged disposal, or your drainline is partially plugged downstream from you sink.

I had maintenance replace the gun on the sink recently.
I hope the gun was unloaded. It sure sounds like you have a partial blockage in the horizontal line in the wall. You can take care of this yourself if you wish. Remove the "J" bend from the trap and send a snake up the trap tail. (see image). You'll hit a bend about 8 inches in but once around that you only have 6 more feet to put out. Flush with a sink full of hot water. For the nsmell I would scrub out the sump in your dishwasher with bleach. Don't just pour bleach in the sump get down there and scrub it.
And quarter a lemon and run it through your disposal. Good luck, Tom

If you don't use dishwasher regularly, it will smell. There is water in the discharge hose that will go bad after few days. Also, there is water inside dishwasher's pump that will smell as well. Any small food particle left in the water after dishwasher was used will rot and smell. Same goes with garbage disposer. Solution: use lots of water when using garbage disposer. Run dishwasher once a week.