If you are someone who doesn't always get great sunlight, one of the simplest ways to fix bad lighting is to invest in a lightbox.
A lightbox is an empty box with all-white sides, and a white backdrop, often with white LED or other lights attached to the top.
Another way to up your image quality is to work with natural light and it's free! Many food photographers use natural light, and it can be gorgeous.
This can become more difficult with food items that come in many pieces, such as a set of cookies vs. a slice of cake.
If you are new to photography, one way to fix this problem is to dedicate your photo session to one type of photography composition.