I need help with concentration and focus. If I drink 1 diet coke every 2 hours, should that help?

Coke won't help. Caffeine or coke won't help with concentration over the long haul. Medically, we would want to test for deficiencies like magnesium, thyroid, b-12, and iron. Sometimes, excess sugars lead to concentration problems. A good diet with vegetables, fruits, and proteins (avoiding fats and carbs) would also help your system. Finally, ask your doctor about attention deficit.