Put out a plate of oreos where 3/4ths of them are "gross"... put thin not-easily detected layers of garlic powder, salt, onion juice, tabasco, fresh ginger juice, (all of these things are strong so a little will ruin the flavor and maybe not ruin the smell.
Also maybe try non-toxic essential oils that SMELL good but taste awful... like just a quarter drop of mint EO on mint oreos... but leave some cookies ok.
Warning: this may cause wet/halfchewed cookies to end up on your floor or table..
Try not to laugh, he'll be on to you;)
Give him a mix of good and bad cookies whenever you give him cookies. He will become VERY untrusting of cookies very fast, methinks..
Depending on his age and stubbornness (his stubbornness seems rather high hehe) he might learn fast or slow...
Then start substituting healthier cookies that are delicious but maybe not so packed with sugar and fat as options which will ALWAYS be good tasting, but a better choice for him.
Ok, honey... you can take your chances with a batch of
oreos... or you can have a couple gingersnaps (graham crackers, oatmeal/raisin crisps, or these
) what do you want?