College FB Star -- Signs Huge Deal At In 'N Out ... I'll Take My Future Animal Style

College football star Brock Hekking takes life with grilled onions and special sauce ... 'cause the former Nevada DE just signed one of the biggest deals of his existence -- at his local In-N-Out.

Brock is expected to be selected in April's NFL Draft ... at least according to Octogon sports ... a huge sports agency that reps some of the biggest stars in the world including Michael Phelps and Steph Curry.

So, when Octogon approached him to sign a contract with the agency ... Hekking -- who became nationally recognized for his sweet mullet -- wanted to make the event special and personal.

Which brings us to the In-N-Out burger joint in Vacaville, CA ... Brock's hometown.

"I went every day after high school. It's where I dreamed of becoming a ball player ... so I thought it would be best to [sign my contract] there."

Here's the question ... what do you order to go with one of the most important documents of your life?