Cover crops are useful when improving soil in the ground, but it's not really the same in containers, where drainage and adequate nutrients are most important. Potting mixes go downhill from the moment they begin to be used, and improving them with decomposing plant material isn't useful. If you want to add nitrogen, just do so with regular fertilizer.
That said, if you want to plant cover crops for aesthetic purposes, or else just to see what will work, try alfalfa (edible and grows well) or scarlet clover, or else try barley.

Agreed - skip the cover crops; and if you must reuse the soil next year ..... moisture is your enemy - try to keep it dry until time to use it again.

Al

Thanks. I must reuse because of the cost involved. I purchased over 80 cu. ft. of potting soil with fertilizer and water retention particles. So now I ask, any recommendations on what to add to the soil to make it better. I will be able to keep it dry.

Be on the look-out for fine pine bark. Mix plenty of the bark into your soil next spring (you want more bark than old soil), along with some perlite & lime, and you're good to go for another year.

Al