Mine do the same thing...it drives me insane! Teach her the 'drop it' or 'leave it' command. Give her a toy, let her take it in her mouth. Offer her a treat while saying drop it/leave it. When she drops the toy, give her the treat & praise her.
Mimi will listen to me, but Momo is soo naughty. He'll run (& stop when there's distance between us), turn his head, look up at me, chew & gulp whatever he had in his mouth.
Grrrr lol.