An adaptation of a couple of different reuses .Cannot begin to list how many people have shown pics/instructables on using bottle caps/lids as containers. Thank goodness it isn't copyrighted! My emphasis is on using in a Geocache.
Step 1: Tools/Materials
This is a screenshot (sorry, I was quickly corrected that this is a picture, not a screenshot, wow...) of the items I used, it can vary by your tools available.
For instance, cutting bottle and pipe I used a pvc pipe cutter, you could also use hacksaw.
I prefer the larger bottles or soda bottles due to the actual top size.
Step 2: Another Set of Screen Shots (I Mean Picture, Oops) of the Tools/materials
You will need 2 matching size bottles, and pvc pipe is optional (but has to be 3/4" thin wall if you do use it)
Step 3: Prepping the Container
1st decide what type of bottle lid to use. I like the larger bottles, if you compare to the smaller 16oz bottles, the lids are too small.
Step 4: Extra Layer, Use As Added Strengthening, or Length
Measure, mark, cut.
Insert inside of bottle lid, determine length you need.
You can see the one camouflaged, I used a longer piece of pipe, and wrapped with camo tape and paint.
Step 5: Glue Pipe and Bottle Caps
I went along both lids where cut, and smoothed over so they would make tight connection. For quick seal, superglue is ok. For water tight, use a silicone sealant.
Step 6: The Hardest Part, Prepping the Rock
Find a large stone, rock, boulder.
Start to chisel until desired depth.
I saw this idea, larger scale, with like a 4" pvc threaded pipe with lid was mounted under a rock. This is scaled down. Hardest part is chiseling out the hole, unless you have something like a hammer drill.
BE SAFE, WEAR EYE PROTECTION.
I'm almost done, little deeper to chisel. Will use some kind of epoxy to hold container in hole.
Step 7: Placement
Roll up your geocache log, place in container. You will have to follow Geocaching placement steps from the website. Find your ground zero to place it and let others enjoy the hunt!