There is no quick fix to improve ANYTHING. There is no magic pill, no magic supplement. If there was, you wouldn't be able to get it without a prescription and it would be heavily regulated.
The best thing is amptle rest and a good, clean diet.
There are no quick fixes for improving stamina. However, there are some things you can do to improve ENERGY. Energy and cardiovascular endurance are two different totally different things although they can easily be confused. Cardiovascular endurance is done through proper training, diet, and rest. Energy can be improved with diet, exercise, and rest, but energy is one component of cardiovascular endurance.
Quick fixes for energy are caffiene. But they won't improve your cardiovascular endurance at all. You can have all the colas and espressos you want, they won't do anything to improve your cardio. They will just perk you up temporarily and then you'll burn out. There are many wrestlers who take caffiene during a meet so they are perked up before the match. A match is 6 minutes long, and it's not for stamina but just to perk you up. However, no wrestler takes caffiene during a tournament where it's usual to have 3-5 matches spread 40 minutes apart or more... That's like signing your death warrant.