If you have bronchitis while sleeping or a dry cough you can try to lay down with your head and shoulders slightly raised using a pillow for example. This may relax you and reduce the amount of coughing allowing enough time to fall asleep.
Warming up your throat by drinking tea, for example tea made from citrus fruits like lemon, can calm you down and reduce the coughing / bronchitis. Taking a shower also has a similar effect of calming you down.
There are also some cough medicines which also make you sleepy. But not all are like this, so you can ask your doctor to give you these kind of medications.
