Bran Flakes is a brand of cereal shown on a TV commercial that appears in the episode "As Seen on TV."
The box is yellow and has pictures of red wheat on it. The name of the cereal is written in all caps and in white text with a light blue outline near the top of the box. Nutritional info and other info is on the right side of the box.
It has bran in it, hence the name. It is mentioned to have a bold new taste.
Role in episode
Bran Flakes are featured in a flashback showing Old Man Jenkins watching the cereal's commercial on TV after he mistakes SpongeBob for a cereal box from the commercial, even saying "What a nice cereal box" after he meets the latter.