Sprinting is a great way to build stamina. It gets the heart rate up very quickly, exercising the heart thus enabling stamina growth. It's recommended to only sprint for four to seven seconds at a time then let your heart rate return to normal before going again. I hope this helps <3
You can combine strength and cardio sessions. Choose exercises using lots of muscles. Fast-paced dynamic activities can help too. Don't forget to stretch, drink water, and have quality rest.
Biking, long walks, swimming, and circle training, where you alternate between using different muscle groups within one round or "circle"