If your hospital is in the tri-state area, there is likely a kosher restaurant or grocery near you as well as a Bikur Cholim room which is usually stocked with food. There may even be kosher food in your hospital cafeteria.
This list can help you find kosher food sources in your hospital.
Additionally, the app called Great Kosher Restaurants will sense your location and tell you which kosher restaurants are near you. Its incredibly helpful when you are in an unfamiliar location.
If your hospital is not in the tri-state area, there may be kosher food near you. You can ask your hospital staff if there is a Bikur Cholim room in your hospital. (You may be pleasantly surprised.)
You may also be able to find a source by googling “Kosher Food Near Me.” If this yields no result you, can try to find out information on the Jewish community near you by contacting the local Chabad house. They should be able to help you with any religious related needs you may have while spending time at the hospital.