Why do airplanes bank sharply to the right after air-to-air refueling?
Fighter jets are very maneuverable, so they may make anything from a shallow bank to a breakaway maneuver. The breakaway is a standard way for fighter jets to exit a formation. It provides a way to safely and quickly gain separation from the other aircraft.

In this case the bank is fairly shallow, but when the aircraft disconnects they are already in a shallow right turn, so the total bank angle is a bit larger.