Yes, adults can sleep on trundle beds. Trundle beds are a great option for adults because they're typically smaller in size than traditional beds, which makes them more conducive to smaller spaces. Additionally, trundle beds are often less expensive than traditional beds, and they can be easily converted from a bed to a couch or vice versa. While some people may find that sleeping on a trundle bed is not as comfortable as sleeping on a traditional bed, most adults find that they can get a good night's sleep on a trundle bed if they choose the right mattress.