Use melted sugar, that'd be more authentic!

I think the point is that the fear of not being able to get it out easily would lead your jaw muscles to clench up. So somebody would have to basically trick you into thinking that the imitation is real.

There's LED bulbs of the exact size and shape but with plastic casings

Open your mouth all the way. Use your fingers to measure it. Do you really think a lightbulb could fit in there?

You could try and find an apple that's about the same size?

Use an ice cream cone. Saves the effort of making some elaborate food thing. And with a cone, you can just bite through it, after the the hard outer, the ice cream is just easy to bite through.

I think the problem comes.up when your jaw locks and its a bastard to move it. I get it occasionally when I'm eating or yawning.