This is something that I've been tinkering with for two days. It wasn't hard to make nor was it expensive. The one you're seeing is the perfected fifth one. The silver one is the first one. The one I'll use for this tutorial is going to be a new from scratch 6.0.
Step 1: BODY
This bottle was found Target but any bottle might work. Now wrap it in duct tape or if you have one aluminum tape.
Step 2: BODY/2
The potato V was insulated with mylar, the gold stuff that they used on the lunar landers. Not needed but I did it and thought it sounded cool.
Step 3: CONE
You can keep the plastic one but I switched it for the aluminum cap found on those aluminum bottle cokes. I used mylar again but it's not needed. I also added a ketchup cup on the top for extra protection.
Step 4: Guts of It
Nothing too complex. The white thing is a icebreakers mint container missing the top. Metal parts not needed but it's just the bottom of a Pringles can.
Step 5: SEAT AND ETC
It is just two layers of cardboard and one layer of Styrofoam. The seat is cardboard that you'll have to figure out base off your astronaut. Don't for get a seat belt, safety first. The fifth picture shows how I added magnets so I can put it on metal stuff. Wrap it all tightly.
Step 6: PUT TOGETHER
Reason its clear is so you can see how it goes together but that's about it. Wrap the container to the bottle tightly for it to be able to float in water. If water gets in the foam will protect the cardboard.
Step 7: OPTIONAL/PARACHUTE
It's a parachute made from a table cover. You can find tutorials for those anywhere. Add a small hole to the cap and slide the end in. For mine I added an elastic string. I don't know why but I did.
Step 8: OPTIONAL/LIGHT
It's basically two foam pieces pressing a led to the battery.
Step 9: NAME IT
Give it any name you want.
Step 10: STRAP IN YOUR ASTRONAUT
Make sure before you do anything strap him/her in. I didn't really add a seatbelt on this one but you get it.
Step 11: GO PLAY WITH IT
Now that it's done you can throw it and watch it parachute back down, do a recover splashdown mission in the bathtub or launch it on a model rocket somehow.