What happens if we accidentally add more (5 ml of 200 mM) sodium pyruvate to 500 ml DMEM cell culture media that already contains 110 mg/ml sodium pyruvate in it (from company)? How will it affect the growth of cells say for example HEK293T? Thanks.
Sorry to tell you that it's not worth to discuss the influence. Just discard, please. Obviously, pH and osmolarity changes are serious ones. The cells are so unhappy. They may be choked within several hours due to the overused energy sources, disturbing carbohydrate metabolism, too. Eventually dying.
Since a salt in excess will make the osmolarity of your medium increase, the liquid content of your cells will flow from inside of them to the media, trying to compensate the increase of dissolved ions.
As said before, discard the medium and make new one.