To get the Barley and Spoiled Blueberries achievement in State of Decay 2 do the following:
Bloaters are the hideous greenish zombies with the big ball stomachs. They will chase you and explode, suffocating you and attracting zombies. Running one over doesn't seem to unlock the achievement and it'll just fill your car with their noxious gas so don't do that!
Shoot them from a distance, either in the stomach for them to explode or in the head to just have them fall down. Don't get too close, whatever you do.