When I was a young'un on Write It!, I'd always give the advice, "If you're blocked, go take a shower." I still think this is true, although you've got to be careful about wasting water and stuff. The shower is a great place to relax and think, get the ideas flowing again. FLOWING LIKE THE HOT FLOWING WATER OF FLOWINGNESS. It has the added bonus of being a place where you can talk to yourself freely and/or act out scenes and no one will know.
I think anyone can attest to the fact that the in-between sleep and awake space always manages to provide some kind of inspiration. You always get your greatest ideas when it's the least convenient to get up and write them down, right? So maybe go take a nap, but take your notebook with you.
Exercise, difficult as it sometimes can be, is another great way to get your brain flowing again. Because it releases all those happy neurotransmitters, it helps your brain get itself cleared up and working a bit more freely, just the way it helps flush your body of toxins. Listening to music while exercising is especially great to get some kind of narrative running. I like to come up with book trailers in my head when I get on my exercise bike. However, if you are at a public place like a gym, you do have less freedom to get playacting or thinking because people will look at you weird. (WHY DOES THAT GIRL LOOK LIKE SHE WANTS TO CRY? Because she's thinking sad and dramatic thoughts about her WIP. Shh.)
A lot of the time, if you're stuck, it means you just need to take some time to push through it. Blocks tend to come more from laziness or fear than anything else. So force yourself to sit down and get working, whether that means writing or outlining or something else. I like to draw sometimes, characters or book covers, if I'm feeling the well running dry. To help readers out, I've in the past listed some other ways I get inspiration and explained how writer's block also can come from not listening to your characters properly. Whatever the case, writers tend to get inspiration at random times and random places, so it's best to be ready and waiting at all times. You never know when brilliance shall strike!
Images via bobvila.com, WebMD, sv.thebbbconnection.com, and smartpassiveincome.com.