What happens to a patient with a coronary artery disease if he is given 1 liter of intravenous fluids in just 2 hours?

Likely nothing: This is a bit more than a usual beverage and you state it is iv. Most will respond by urinating. Someone with a low blood pressure to rise or dehydration will feel better. If the person is already overloaded or in heart failure they may feel worse or get short of breath and need medication. For someone in shock this may not be enough fluid. So it depends on more than coronary disease.

Depends: If cardiac function is normal, blood pressure is controlled, and there are not symptoms of congestive heart failure, 1 liter of IV fluid should not cause much symptoms.