i don't know about coffee grounds i heard that b4 HOWEVER if you take a fresh jar of peanut butter and scoop out the middle of it and slide in a sak of killers then put most of the scoop back on top of it twist the lid back on and your good to go dogs can't smell through the peanut butter it has been tested by overseas travel and domestic mail. bty keep the silver tin of the peanut butter jar so it looks unopened