Thermometers all over the UK are soaring as the streets are invaded by men with polo shirts half tucked into their shorts. It's hot. Super-hot. And, God knows, we don't know how to handle it.

Local councils and the NHS are alerting parts of the country of a heatwave, suggesting that people stay inside for the middle of the day, when the temperature will finally rise to summer highs – there's a possibility it will peak at 35C today (19 July).

But the main advice stays the same – stay in the shade, be wary if you have breathing difficulties and keep hydrated. Here at IBTimes UK, we take our water very seriously. Previously, we've tackled the age-old question that has plagued many a dinner table: does expensive bottled water really taste any different from tap? And now, we seek to answer a new, topically heat-related question: is fizzy water more refreshing than still?

The quick answer is no. It's water.

Is expensive water really any different?IBTimes UK

IBTimes UK asked Lucy Jackman, spokesperson for the British Dietetic Association, whether there would be any reason to choose carbonated water over still when you're trying to stay hydrated: "There's not actually any difference in terms of hydration – the electrolytes in normal carbonated water would be exactly the same."

As an interesting aside, the reason we enjoy carbonated water might come as a surprise. A study from the University of Southern California (USC), mentioned in this piece from Popular Science, suggests that the CO2 in carbonated water triggers the same pain receptors in the nasal cavity as spicy food.

So why do we enjoy something that make us feel (very mild) pain? "It may be a macho thing," one of the USC authors suggested. Though an earlier study showed that carbonation makes us perceive drinks as colder than they actually are – if you're looking for a refreshing drink on a hot summer's day, maybe the perceived cooling sensation of carbonated water could make it seem like a more cooling choice.

In all of this, we've neglected one stark and contentious question. Is soda water the same as fizzy water? You can certainly swap them for that midday gin-fizz but there is a slight difference – soda water usually contains a few added minerals – as Jackman told us: "There might be added sodium and different vitamins," whereas carbonated water is just water that's been carbonated, hence the name.

People in Amsterdam cool off in fountain
People in Amsterdam cool off around a public fountainGetty

"It's just important when it is this hot to make sure you're getting adequate fluid." If you're not a big water person, Jackman suggests adding chopped-up fruit to change up the flavour. As for the much-hyped coconut water: "There's not been that much scientific evidence to suggest that it's actually better at hydrating you than your normal water or electrolyte drinks."

If you're planning on doing sport in the sunny weather the recommendations are slightly different; you'll end up sweating and losing a lot of the electrolytes so to keep up, Jackman says you might want to replace lost electrolytes with an isotonic drink.

"If you're just an average person... make sure you get enough water in in the day, six to eight glasses a day would be around recommended." Though Jackman added that there is one possible downside to carbonated water – the bubbles make you feel full: "You might find that people are actually drinking less because they're feeling quite full up."

So happily hydrate with carbonated water – just make sure you're still drinking the recommended amount.