Drop your phone down inside with music playing and it'll amplify it.
Poke a pen tube diagonally in about a quarter to a third of the way up, partially fill with water and you've got yourself a bong.
Poke a small hole right near the bottom, spray an aerosol in and put the lid on, then hold a lighter or a match to the hole and surprise your mates.
Cut a cardboard disc the same diameter as the ID o the tube, fill it with money, drugs, small bottles of alcohol, sex toys, knives, USB's, etc, slide the disc in, put a few Pringles in and put the lid back on. - Hidden storage.
Get 25 of them, paint 22 green and 3 of them red/brown, stick paper discs with the numbers 1-25 on them inside the lids, fill them with tasty treats and arrange the 22 green ones in a triangle with the 3 red ones on the bottom, glue it all together and stand it up. - Giant Christmas tree shaped advent calendar