clean out all the crumbs, then steam clean it to loosen up the dried up liquids and stains. Then sponge it with hot soap water and dry. Voila
Cheap products work for me as well.As per my opinion, you can high quality dishwasher to clean your microwave and you can use soft towel to with cleaner. You should avoid any cheap products because it will not work much more. Which is product do you use to clean your microwave?