It never fails. You turn on the TV, start a new podcast, open a web browser, or walk through the supermarket, and you’re bombarded with ads pushing quick fixes to help keep you going in a demanding world: an immune boost here, a hangover cure there, a supplement for your hair or skin, or a little something to help you relax at night. What’s the evidence that these drink mixes, gummies, probiotics, and powders deliver on their promises? We took a look.