Courtney Stodden Chows Down on Veggie Burger in Tiny Bikini

Courtney Stodden must've been watching a bunch of old Carl's Jr. ads ... 'cause she stripped down to a tiny bikini and bit into a veggie burger just like the old commercials.

The reality star and internet personality shared a couple of snaps sizzling more than a patty on the grill ... wearing a tan bikini top and bottom while biting into the side of the behemoth burger.

She added a video to her post, too ... getting all messy as the toppings on her burger fell down her front, dirtying her chest.

Stodden wrote in her caption that she's celebrating National Veggie Burger Day ... saying veggie burgers are great for bold women who have no shame in choosing avocado instead of a slab of beef.

She added, "Salty. Sultry. Sustainable. For the baddies with brains, hearts, and a plant-powered bite" ... so, it seems clear she's trying to see if sex sells sustainability.

Stodden's a well-known vegetarian, BTW ... saying years ago she "never felt right eating animals." She's pushed the vegetarian lifestyle for animal rights agencies like PETA.