If you want something thick and pongy off the supermarket shelf, Marmite or Bovril work. Thinner ones such as Nam Pla (Thai fish sauce) or Oyster sauce are also good. All cheap, all work....but of course you could hardly call them home made.
Other than that, any old boilie base mix or ingredients for same you have laying about, mixed with liquid fish protein or similar, to make a good sludge.
Glycerin is a commonly used base for commercial glugs, so any old flavours, dips, or any of the stuff previously mentioned can be added to that to make a fairly viscous glug. You can buy glycerin from Boots for not a lot.
Corn steep liquor and liquid molasses are used to enhance horse feed, so you can buy this in large or small quantities from equine suppliers for a fraction of the cost of that sold in little bottles as attractors in angling shops, and that can be added to glycerin too. Take your pick, experiment...great fun.
Cheers, Dave.
