In case you were using rudder and opposite aileron to maintain wings level, then that is another story:
You would be skidding, now, and turning (heading would change because of the rudder creating the slip angle) therefore the ball will be pushed out of the turn by centrifugal force. The larger the skid, the more the ball, and your body, will be pushed. Centrifugal force alone acts on the ball. Well, gravity does, too, but has no effect in the ball indication.
Coffe will spill, too...