I found the tutorial here. I adjusted the size to fit my water bottles. The author made hers to fit purchased water bottles. I wanted mine to use with our reusable water bottle. I am giving the dimensions for mine. If you want one to fit a purchased bottle of water follow the link for the tutorial.
First out of cotton fabric I cut two rectangles 9 inch x 12 1/2 inches. And two 4 inch circles.
I got the measurements by measuring the height of my water bottle and adding an inch for seam allowances. I measured the circumference of the water bottle and also added an inch for seam allowances. I measured the diameter of the water bottle and added 1/2 inch for seam allowances for the circle.
Next I cut out the Insul-Brite. I cut this into an 8 inch x 11 1/2 inch rectangle. And a 3 1/2 inch circle. The Insul-Brite is cut to the size of the water bottle.
With right sides together sew the top of the carrier in an 1/2 inch seam. Press open and place the Insul-Brite inside. Butt it up against the seam. Fold the carrier back over and line up the edges.
Next sew the side seam of the carrier. I followed the tutorial by making a french seam. This is done by bringing the wrong sides together and sewing a 1/4 inch seam. Then turn the carrier wrong side out and sew a 3/8 inch seam. This encloses the raw edges of the previous seam. Overcast around the edge of the circle. Make sure you also mark the side that has the shiny side of the Insul-Brite.
Pin the circle to the bottom of the carrier. Make sure the Insul-Brite side of the circle is facing the wrong side of the bag. When you pin it to the bag this side will actually be facing out. Sew the circle in place using a 1/4 inch seam. Overcast the edge of the seam.
Turn the bag right side out. Cut a piece of ribbon 42 inches long. The author sewed twill tape to the back of the ribbon to give it more structure. I found some iron on hem tape in my stash. So I ironed that on to the ribbon and then topped stitched along both edges of the ribbon.
Sew the ribbon on the inside of the carrier on opposite sides. I folded over the bottom edge and sewed a 1/2 inch square to secure it. Your water bottle is now complete.
My kids loved these. They slung them over there shoulders and toted them around all day. We tested them out today and I was totally amazed. We filled the water bottles half way with ice and filled with water. Five hours later the water bottles still had ice in them. I have an insulated water bottle and my ice melted in mine after an hour. Seven hours later my son said the ice has melted but the water is still cold. Granted it is not 95 degrees Fahrenheit out but if after 5 hours they still had ice in them I am sure they will keep cool during the summer as well.
Now I am going to have to make myself one. I think I might make a large picnic bag with Insul-Brite in it to keep our food cold!