As a teenager (male) with raging hormones I figured this out and has been my fav forever—and I’m now 71. Here’s my way (and it’s fantastic—for me): Put enough tap hot water in sink or other container then place hot water bottle without the screw in stopper so the water goes in and bottle submerges. This warms the outside and inside. Yes, you can also just run straight tab hot water over the bottle but it’s not as good.
After few minutes, fill the bottle with hot water (don’t use boiling water) about half way so you can fold in half and has a little air in it—then while folded in half put the screw in stopper.
Next, open up flat and put lubrication on side facing up, then wad up some toilet paper and put top middle of bottle, then fold in half. Then go to the bed where you have multiple pillows stacked, and a small towel is folded in half between two pillows where the water bottle goes between the towels and pillows. Next lube you cock up then lay on the pillows and work your cock between the folded water bottle, then fuck away. Depending on the amount of pillows you stacked that’s comfortable for you, it feels like your on a body as you can hug accordingly, and your cock feels warm and engulfed—even the raised pattern on water bottle ads to the sensations. Also, with being on bed and multiple pillows there is less pressure on water bottle and I have never had one break on me. When you cum it is caught by the wadded toilet paper in the folded water bottle. Clean up is easy then, when you get your strength back to get up.
It seems to take more time preparing but feels so close to the real thing. This way gets me to orgasm the fastest of any other way and is so fantastic. For me none of those toys including flashlights come close. Plus it’s so simple—and not expensive. And when I get it just right, it’s equal to or better than the real thing. Hope you’ll find it so too. Enjoy!!