A line is a straight, one-dimensional object that extends for infinity. There are no endpoints for a line. A line segment is a section of a line. It has specific endpoints. Since a line only has one dimension (length), real world examples aren't true line segments. All objects have some amount of width or depth. However, that doesn't mean you can't illustrate the concept. Certain foods show the basic idea of a line segment.
There are line segments already in your pantry. Uncooked spaghetti noodles are ideal examples of line segments. When cooked, spaghetti is still a line segment if it is straight. Curving the noodle or twirling it around your fork removes it from the line segment category. Fettuccine and angel hair are also line segments of varying widths. Asian eggs noodles are line segments from a different part of the world. However, macaroni, corkscrew pasta and packaged ramen noodles are not line segments because they are not straight.
Line segments can also be found in the candy aisle. Licorice is a line segment if it is kept straight. Peppermint sticks are also line segments (but not candy canes, because of the curved end). Look at your favorite candy bar, chances are it is a line segment as well. Pace yourself on enjoying these line segments, though. You don't want your math lesson to result in a visit to the dentist.
With a knife and some ingenuity, it's possible to make line segments out of all sorts of food. Slice grilled chicken into strips. They may be short, but they are still line segments. Dice vegetables like celery, carrots, or rhubarb into straight sections. Throw a line segment dinner, where all the foods are line segments. Remember, the line segments have to be straight and have only two distinct endpoints. Let your stomach be your guide.