The craft of building models of boats and other objects inside bottles dates back centuries. The work still requires a lot of time, care and patience. Much of it involves using tweezers to place parts inside the bottle. The 21st Century version might be to build a mobile phone inside a beer bottle. This can't be done the same way a model ship is built inside a bottle, however, because cell phones have so many intricate parts and pieces. Other techniques are needed for this type of model.
Cleanly break the bottom out of the beer bottle. This can be done by filling the beer bottle most of the way with water or beer, then hitting the open top with a slightly cupped palm over and over again. The air pressure you create on top of the liquid inside the beer bottle will create equal force on the bottom of the beer bottle. The bottom will finally break and fall off cleanly. Hold onto the bottom of the bottle for later.
Carefully dry out the empty beer bottle, being sure to not cut yourself on the broken glass on the end of it. Place a small, thin cell phone inside the bottle.
Put on gloves and goggles and the use a blowtorch to carefully melt the beer bottle bottom back onto the end of the beer bottle with the cell phone. You might need to melt more glass around the bottom of the bottle to fuse the two sections together more firmly.
Consider adding sand or some other items inside the bottle as well. Try not to move it once this added weight has been placed inside the bottle, because the glass of the bottle is weak and might break.
When you knock the bottom out of the bottle, make sure you stand over grass or a soft surface so the bottom doesn't break when it hits the ground. If it breaks, it will be difficult to reattach the bottle's bottom properly. Always wear gloves, goggles and even a breathing mask when using the blowtorch to melt the glass of the beer bottle, because this can be hazardous.