Some of our flavours without the 'alcohol-free' tag contain trace alcohol (<0.1%). Small amounts of pure ethanol are used only for its chemical property of allowing natural fruit oils to mix with slush without separating. This small amount could not cause any perceptible intoxication even when drinking large amounts of slush. Many common foods have some low alcohol content: bananas, grapes, oranges, apples, bread, vinegar can contain up to 0.4% alcohol.
Further reading on the 'halal' nature of alcohol in flavoured products is available here:
https://www.halalcheck.net/en/wiki/Alcohol-in-AromaFlavours Coming Soon...