I’ve done a Coopers Irish Stout and a Cooper Ginger Beer which I’ve bottled in 500ml bottles using Coopers Carbonation Drops. Coopers recommends 2 carbonation drops per 750ml bottle, I’ve used 1 and a half carbonation drops per 500ml bottle and it has worked well for me.

Use a knife to cup the drops in half, i tried scissors but that resulted in carbonation drops flying around the kitchen.

One bag of carbonation drops should do a 40 pint kit and you can get a bag for about £2.50.