Can bearded dragons eat slug

not really, if you did give your bearded dragon a slug it would probably get either very very ill or even die.

I wouldn't advise giving bearded dragons slugs or anything that you catch infact as insects from the wild can carry disease, even if they are from your garden.

Bearded Dragons are best cared for when they are given good live food bought from a pet store, such as locoust or crickets