Healthy dog food???

What are some healthy things that I can add to my dogs dry dog food to make her want to eat it more? She is a healthy weight and does eat, but not as much as she should eat. She should be eating like 6-8 cups a day and she will only eat like 4 cups a day. Again, she is healthy and everything, I just want her food to be more appetizing. Wet dog food makes her sick.

*added*

She needs 6-8 cups because she is a giant breed dog. She is a Dane.