Daniel Pink argues that breaks are drastically under-researched. The best ones are active, outdoors, and social: take a walk with someone, leave your phone behind, don't talk about work. Movement beats sitting still, and outdoor beats indoor.
The science of breaks is where the science of sleep was 15 years ago. We should be taking more breaks, and we should be taking certain kinds of breaks. We should be taking breaks where we're moving rather than stationary. We should be taking them outside rather than inside. We know from the research that social beats solo in break-taking, so take a break with somebody else. And we know the importance— this is urgent— of full detachment. So when you take a break, leave your phone behind, don't talk about work. Take a walk outside with someone you like, leaving your phone behind and talking about something other than work. I'm convinced it'll be a performance booster.