First, I dyed the T-shirt a yellow-orange.
Next I cut out all the pieces and layers. It has 4 layers - the outside T-shirt, a thin batting, a T-shirt lining, and a clear plastic layer. The plastic layer will keep the any wetness on the outside of the bottle from soaking through the fabric and possibly damaging the cell phone.
So here's the finish product. It has an elasticized opening to accommodate varying sizes of bottles.
It's great to take on a walk or a short hike that doesn't require a backpack full of supplies!