Step 1: Materials/Tools
An empty tube of caulk/filler/sealant, a long stick and a hacksaw. Chop off the end with the hole in it about one centimetre down (this will be the needle end of the syringe) and poke out the internal bung with the stick (this will be the blunt end).
A plastic bottle (I used a two litre lemonade) and some sharp scissors. Cut the top and bottom off the bottle and roll it to fit the ends of the capsule. Add a layer of sellotape to hold it, and glue one end in place.
A caulking gun (presumably you'll have one around, if not then they're a few pounds at a DIY store).
A clear plastic straw and a bolt (optional but I think it looks quite nice). Cut the end of the straw at a slight angle with the scissors and screw it into the bolt if youre using one.