Put 50ml coconut rum, 100ml pineapple juice, 25ml gin and 50ml cold water into each jam jar.

Stir, then garnish each one with a piece of watermelon and a couple of coriander sprigs, squeezing the leaves a little bit first before dropping them into the jars to help release the flavour. Screw on the lids and chill or set in ice buckets until needed – they will keep well for 4-6 hrs.