Feed the intended target anything from the following fast food chains, (feel free to improvise from the given set list of foods below as these institutions have more deadly poisons at their disposal):
McDonald's: Big Mac and chicken McNuggets;
Taco Ball: Everything on their menu;
White Castle: sliders;
Any frozen dessert that's gluten free, sugar free, dairy free, fat free is soul crushing so it may not kill a healthy human being but it will definitely convert the consumer into an undead zombie which is worse then death.