About 20 heads of elderflowers -creamy ones not ones that are turning brown
700g white sugar
2 tablespoons of cider vinegar (or distilled or white wine vinegar)
Peel and juice of 2 lemons
Put everything into a large bowl with 1 gallon of water and give it a good stir to dissolve the sugar. Cover the bowl with a tea towel or mesh cover (not cling film as it needs to breathe) and leave for 24 to 48 hours in a cool place and then strain into plastic fizzy drinks bottles.
Keep it for a week or two so it builds up some fizz and drink within two or three months.
Read more about making Elderflower Fizz here