Swimbladder disorders are from a # of factors: genetic/congenital (born that way), rapid temperature changes, bloat/constipation(overfeeding), injury (fighting/too "harsh" of a waterchange), bacterial.
Would help to know which type of fish (certain species are more prone to SB disorders). How much do you feed the fish? What is the water temp? How often/how much do you do water changes? Any other behavioral signs (ie flicking/rubbing/darting, spots on the fish, finrot or other issues, clear white mucousy poo).
Difficult to suggest treatment if you dont know the cause. Most SB can clear on its own with stable water temps, clean water and not too much food. In some instances the fish does not recover, and as pathetic as they seem, can live a mostly normal fishy life (if they can eat and swim rather normally). Usually is NOT contagious to other fish.
A little more info from you would be helpful regarding type of fish, diet, water parameters, waterchange routine, water temp and tank mates, along with other signs of illness.
All the best
CHEERS!