I’m fairly sure you would not want to break them down so your body could absorb whatever is in them more easily.

I think the problem is that any acid strong enough to break down the bonds of plastic would be too strong to comfortably sit in our stomachs.

Maybe you could add some of those plastic eating bacteria with like an artificial fecal transplant? Not sure what the consequences of introducing those to a gut biome would be.

Add plastic eating bacteria to our gut biomes maybe?

Surely we would not have our bodies so full of microplastic if our stomachs could destroy them.