When we've had our dog out for a walk and he snaps something off the ground into his mouth, we just say, "LEAVE IT", and his mouth pops open like a PEZ dispenser. I'm not bragging, I'm just saying that with practice, they do learn. When we had his treat in our hand and popped it shut with the command, we did this about 5 times and then gave him a break. We did it for about 3 days, and he will always drop what's in his mouth.
Brian
