The Mack truck, which includes the singer's autograph on the sun visor, was on display at Perimeter Mall last week.
Proceeds from the auction will be used to help fund programs offered by Camp Southern Ground.
Founded by Brown, Camp Southern Ground provides summer camps for children and programs to help veterans transition to civilian life. They expect to serve 600 children next summer and 224 veterans next year, according to Camp Southern Ground spokesperson Beverly Rhodes.
“It's incredible to make something on this level of quality, to execute something truly excellent, that benefits a higher purpose. This auction will directly help us serve more kids and more veterans,” Brown said.
"Our goal is to provide experiences for children and veterans to recognize and magnify the unique gifts within themselves in order to positively impact others," said Mike Dobbs, CEO of Camp Southern Ground. "Our veterans have operated under the highest of callings to serve and protect the freedoms of the American people, and we are dedicated to care for them upon their return home."
Friday, the highest bid for the truck was $160,000. The auction ends Nov. 30.
Other notable features on the truck include leather-wrapped seats with the Zac Brown Band logo, and flooring in the cab that was taken from the band's studios in Nashville, Rhodes said.