What are the best lunch boxes for adults that don’t leak or feel childish?

I’m trying to get better about bringing lunch to work instead of buying food all the time, but I need a lunch box that actually makes it easy.

I don’t want anything huge or overly “school lunch” looking. Just something practical for adult lunches that can handle normal meals like rice bowls, pasta, salads, sandwiches, leftovers, fruit, snacks, etc. Leak-proof matters a lot because I’d rather not discover soup or dressing all over my bag.

I’m also not sure whether to go for a bento-style box, glass containers, stainless steel, or an insulated lunch bag with separate containers inside.

For people who regularly bring lunch to work, what setup has actually worked best for you? Anything that keeps food fresh, doesn’t leak, and is easy to clean without becoming annoying after two weeks?