We all go through more plastic bottles in a life time than we would like to admit. Here's a fun, and easy way to reuse them. All you will need is scissors or an Xacto knife and some fine sandpaper (or a nail file will do).
-Cut the top off of the bottle.
-Cut one side down lower while leaving the other side higher for a handle.
-Cut a hole in the handle side
-Cut a few drainage holes out of the bottom (optional but helps prevent water and bacteria from hanging out in your sponge holder).
-File all edges down
-Hang from your sink.
This is a fast easy way to hold your sponge where you need it and off of the counter. The best part is, when you throw away the sponge and replace it, you can also replace your sponge holder so that the old bacteria doesn't have the chance to infect the new sponge.