Reviewing words when you're super busy

I've had such a long week at work and it's getting hard to keep up with my vocab. I try to do a little bit every morning while having coffee but I keep missing days. Do you think it's better to do five minutes every single day or just one big session on the weekend? I really want to keep going but I'm just so tired lately and my brain feels full. Any tips for a simple routine would be great!