Laundry sheets are made from polyvinyl alcohol which is a plastic and potentially damaging to the environment [0].
Edit: According to a study by Michigan State, PVA will break down completely if certain microbes are available [1]. Which is not always the case.
[0]https://pmc.ncbi.nlm.nih.gov/articles/PMC8199957/ [1]https://cris.msu.edu/news/trending/trending-polyvinyl-alcoho...