foam tunnel?

The foam could cause blockages if they eat it. Try the same thing with cardboard instead. Good idea though!

Ditto Inle_Rabbit -- they'll eat it and you'll have sick pigs and an enormous vet bill. You can do the same thing with an oatmeal box, or buy a Chube for them.

I agree, foam isn't good for pigs and they chew everything so chances are they would, at some point, ingest it. Foam tends to expand when when so that's a double whammy for them. Also, the remnants of the hot glue would not be good if they happened to chew that part of it.

Cardboard would be better or wood - even better.