The coin in a bottle is a classic magic trick. It might not be David Blaine's playing card through a car window, but it is a cheap and easy way to impress people. There are two main tricks. One uses a plastic bottle and a magnet and one uses a stunt coin and a glass bottle. Both are easy to perform with a bit of practice.
The magnet and the plastic bottle trick
Cut away the labelling from the plastic bottle so nothing is obscured.
Put the coin on the inside of the bottle cap and hold the magnet on the other side. The neodymium magnet is very strong and will hold the coin in place. Screw the cap back on and keep your hand over the top to keep the magnet in place. It might be a good idea to use double-sided sticky tape to attach the magnet to the palm of your hand.
Ask a member of your audience to give you the same type of coin you've secretly put in the bottle.
Hold the bottle in one hand and have the coin on the palm of the other hand. You are going to slam the bottle down on your other palm and dislodge the coin in the bottle from the magnet. This will make the coin appear to have been passed into the bottle. However, this still leaves the other coin on your palm. So, as you slam down the bottle palm the coin and magnet. Alternatively angle your hand with the coin up slightly so the coin slides down your sleeve. With practice you will be able to do both the bottle slam and the coin disappearing seamlessly.
Hand the bottle over to your audience to inspect. As their attention is taken by the coin in the bottle discretely pocket the magnet and coin.
Cut away any labelling from a glass bottle. Alternatively you can ask someone to donate a glass bottle.
Ask for a quarter or whatever real version of the stunt coin you have purchased from a magic shop.
Challenge members of your audience to put the coin through the glass bottle neck. They will be unable to do so.
Wrap your flexible coin-wielding hand around the bottle neck. Put the real coin against the side of the bottle with your other hand and talk the audience through what you are going to do. This is the perfect time for a good joke because you need to distract them from what you are really doing. As their attention is taken by the real coin and your spiel, discretely push the flexible coin into the bottle neck.
Tap the real coin against the side of the bottle three times and on the third time palm it. At the same time twist the bottle so the flexible coin falls inside. While their attention is taken by the coin in the bottle, pocket the real coin.
With practice on trick 2 you can get the coin back out of the bottle again for an extension of your trick. You can buy the flexible coins at magic stores and online.
In the first trick you cannot give away the bottle for initial inspection because it would break the link between the magnet and the coin. There are many alternative methods for this trick.