For me, writer's block is a very real thing with varying degrees of severity.
There are times when 10-15 minutes of 'free-writing' frees the muse enough for me to get back into the story. Other times, I have to step away from the computer completely then pick up a pen and notepad to jot thoughts I have for the scene I'm struggling to write. That is truly free writing because it removed the pressure of that blinking cursor.
When I free-write, I usually write about where the last scene left off, how the characters felt at that point, what they need to do next, how the setting will feel, what will be the emotions they need to experience... I won't spend too much time on any one thought. It's just jotting, nothing solid until the muse becomes engaged. I'm always amazed at how well this works.
But when it doesn't...
I exercise. Trust me, it's a last resort. I could tell you I nosh and drink tons of coffee (which I do), but that's more a way to procrastinate than to overcome writer's block.
Still, I have a compact treadmill in my living room and when I am truly stuck and cannot work through a scene, I'll get on the treadmill and just start walking. I'll think about how I brought the story to the point where I'm stuck, trying to feel the emotions of the scenes. As I think more about it, I pick up more speed on the treadmill and it clears my mind. I don't know how it works but it does. Sometimes I'll come away with only one sentence, a transition, but that might be all I need to get going again. Sometimes, an error in a previous scene suddenly becomes clear. And sometimes the answer becomes so clear I wonder why I was stuck in the first place. I'm not sure how running does that for me, but it does, so I do.