17p bottle of carbonated water from Asda(other supermarkets are avaialable), a couple of limes(or any flavoursome fruit), blitzed or juiced, pour the juice/pulp in, chill overnight, or indeed stick it in the freezer, and Bob's your auntie, nice refreshing chilled drink that will be fine the next day.
I don't drink, but driink a ton of Soda water & Lime in the house and when we do go out, and with the wife being a cook, she came up with alternatives to buying the sweetener filled rubbish, so it cuts down the Coke, and other juices.
Some large Oranges are another good one, gives it just a hint, like a faint whiff of Orangina.
Pomegranates too work well.
I bet the "naturaly sources flavourings" are sweetened at source for the juice you linked to.