Here are the locations for all the ingredients for The Krabby Patty:

These don't need to be in order as far as I'm aware.

BUNS: The Buns are located in the first stall in the toilets (750 to unlock the door). Use a grenade/explosive round to blow the door off. The Buns are sitting on the toilet seat. (sometimes the door will come off but you will still be stopped by an invisible door, just keep throwing grenades/explosive rounds until you can get through to pick them up). In the second stall if you go prone, you can activate one of Spongebob's socks.

PATTY: The Patty is hidden inside the pipe that leads from the roof into the kitchen (1000 to unlock the door). Aim at the top of the pipe and after shooting, you will hear a clunk, then proceed to shoot at the bend in the pipe to hear another clunk. The patty will now be on the grill.

CHEESE: The Cheese is located under the far left table when facing into the Krusty Krab (With your back to the entrance door/Quick Revive). You can grab it by standing over the drink on the table and pressing the action button. (Listen out for the pop to confirm you've got it. You may have to move around the table a bit to get it)

LETTUCE: Shoot the cash register to open the drawer. The Lettuce is sat inside.

ONIONS: The Onions are on the shelf in the freezer (1000 to unlock the door). To the right of Double Tap on the floor is one of Spongebob's socks.

TOMATOES: The Tomatoes are in Mr Krabs' office (3000 to unlock the door) on the left side of Pack-A-Punch under the window frame. This one can be kind of awkward to get but if you go prone it's easier. On the right of Pack-A-Punch is the third and last of Spongebob's socks which will activate the Easter Egg song.

KETCHUP/MUSTARD: The Ketchup/Mustard bottles are on the far right table when facing into the Krusty Krab.

Once all ingredients have been gathered, you can enjoy a Krabby Patty fresh off the grill! I believe this is supposed to give you a perk once completed and I didn't but that could just be a bug on my end. also Still No Pickles!!

Enjoy! See you at the Chum Bucket!