Demand exact change, and tell them that you're keeping any extra as gas money/tip since you're acting as the delivery service. That should eliminate half who never have change or only have 10s and 20s.
Next purposely confuse who asked for what special treatment.
By the third day you shouldn't be asked again.
Of course I wouldn't expect your co-workers to be the most friendly to you after you do this either.
Another option is to eat a late lunch (if you get a choice of when to go) or simply sneak out when no one is looking, or have your own lunch delivered (you never left so they can't get you there, and you "forgot" to ask anyone before you ordered).
Next purposely confuse who asked for what special treatment.
By the third day you shouldn't be asked again.
Of course I wouldn't expect your co-workers to be the most friendly to you after you do this either.
Another option is to eat a late lunch (if you get a choice of when to go) or simply sneak out when no one is looking, or have your own lunch delivered (you never left so they can't get you there, and you "forgot" to ask anyone before you ordered).