HELPP!! i have a german shepherd that knows all his commands but only does it when he wants to.. what do i do!?

i make everything fun and exciting as possible but he doesn't even seem to care. he knows all of his commands sit,stay,heel,down,&speak but doesn't want to do them. i have tried every trick in the book to make him do his commands but none of them work. i have spent alot of money on dog trainers, e collar, treats/food, etc. none of them work...