You could go buy a foldable (and prettier) portable dog water bowl for $10-$15 or you could make one in less than 30 minutes and do some recycling too.
Step 1: Materials and Tools
Flexible Plastic Sheet at least 28cm x 28cm
Piece of scrap wood
I am using some housewrap that I got from the throwaway pile at at local construction site. It feels like fabric; is light, watertight, and strong. It is used in the same way that Tyvek is. (I do not know if Tyvek would work for this project).
And the following tools:
Step 2: Measure, Mark, and Prefold
2. Make a mark 7cm and 8.5cm from each corner. (these marks will be your folding guides)
3. Cut out the square.
4. Use a straight edge as a guid to make a fold. Use the marks that are closest to the corner, and fold inward. Make this fold on all 4 sides.
Step 3: Plastic Welding
1. Heat the soldering iron
2. Place aluminum foil over the area to be welded together.
3. Move the iron over the area where you wish to make your joint, melting the pieces together.
I use the clamp to hold my piece of scrap wood which is my welding surface.
Practice on some scrap pieces. Use the flat side of your soldering tip. Also fold the Foil in half in order to minimize the chance of fouling the soldering iron with melted plastic.
That is the basic technique. Now we start by tacking corners.
Step 4: Folding and welding One.
2. Quickly use the soldering iron to make a small tack weld at the mark
It is very important to match up the inner marks. It creates the inward lean that the bowl has, so that water pressing against the walls will make the bowl stand up.
Step 5: Folding and welding Two.
2. Fold the top of the diamond down underneath the rest of the corner into the little pocket that was created. (do not fold it into the bowl.)
3. Place your aluminum foil over top, and weld it, making sure that the corners are tacked down.
4. Repeat for each corner.
You have finished making the bowl. You might want to wet test for leaks.