By the time you read this, my head will be thump-thumping – but this is not a standard-issue New Year's Day hangover. No. My New Year's resolution is to finally give up my addiction to two liquids that are trashing the lives of some of the poorest people on earth: bottled water, and Coke. In 2009, I'm determined to lose my bottle.

There's nothing more tempting than to imagine our luxuries appear fully-formed on the supermarket shelf. It seems they come from nowhere, and when we toss them away, they disappear back to nowhere. It's disconcerting to break through this haze and trace them back to their origins. How can something so ordinary and omnipresent – something we all glug down daily – be destructive? But I have finally forced myself to read two new book-length exposés of my favourite drinks.

Since I was a teenager, I have thought drinking water comes in bottles. I don't know when I stopped using the tap. I never paused to think that it costs 10,000 times more to drink from bottles, or to read the shelves full of studies showing that tap water is just as healthy and impossible to tell apart in blind tastings. But I am not alone. Globally, we spend $60bn (£41bn) a year on bottled water. Its sales now surpass beer and milk.

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In her book Bottlemania, the investigative journalist Elizabeth Royte traces one of the great scams of our time: why are we paying a fortune for something we have running almost-free into our homes? In 1929, Charles Kettering, the director of General Motors Research, outlined one of the rules of modern consumerism: "Keep the consumer dissatisfied." If the customer is happy with what they've already got, where's the profit? So the bottled water industry began to promote a series of myths. They claimed tap water was filthy, when in the US and Europe it is the safest drinking water on earth. They claimed you need to drink eight glasses of water a day, based on a garbled misreading of a creaky 1940s study. They falsely promised better health and taste.

If the only people being suckered were those of us dumb enough to buy the bottled water, this would be a minor-league scandal – but look at one of the primary sources of mineral water for the developed world: Fiji. Every day, a million litres of freshwater are pumped from an aquifer beneath a rainforest on Vitu Levu and shipped 10,000 miles to Europe and to the US. "This water may come from one of the last pristine ecosystems on earth," the adverts coo – without mentioning that it also helps to destroy it. By the time you factor in making the bottles and shipping this heavy liquid half-way round the world, every bottle of mineral water is – in effect – filled a quarter of the way up with petrol. The fizz might as well be greenhouse gases dissolving into the atmosphere.

And what of the people on the island of Fiji? While we merrily sip their water, a third of Fijians have no clean water at all. There are regular outbreaks of typhoid and dengue fever on the island, culling children and the elderly first.

The bottled water companies claim it is justifiable to take these people's water. They say they are carbon-neutral because they buy "carbon offsets". But as I've argued before, the evidence shows carbon offsets are a con – a way of salving our consciences, not the environment. Then they say they put money back into Fiji. But last July, the government there decided to introduce a tax on the bottled water being shipped off the island to pay for clean water for ordinary Fijians. The bottling companies went ballistic and threatened to shut down factories. The government gave up. The typhoid continues.

And what of my caffeine fix? I would have it running intravenously into my veins 24/7 if I could – but the comedian-activist Mark Thomas has persuaded me, in his excellent new book Belching Out The Devil: Global Adventures With Coca-Cola, that I have to find a different dealer to Coke.

In Carepa in north-western Colombia, Coca-Cola has a fairly typical bottling plant. Until 1994, the workforce was unionised, and successfully bargained for the basic workplace benefits we all want: bonuses, overtime and healthcare. But the corporation wanted to cut costs – and around the same time, the armed gangs arrived. The far-right militia the AUC presents itself as "the defenders of business freedom" in Colombia – they massacre trade unionists.

Soon after they showed up, Enrique Gomez Granado – one of the Coke-plant union leaders – was shot in the face on his doorstep, in front of his wife and kids. Five more union leaders were hunted down and murdered. There was, as Thomas puts it, "a campaign against the union at the Coca-Cola plant". The workers at the factory claim their plant manager would sit outside the factory with AUC paramilitaries, laughing and joking with them. Once the union was destroyed, the managers of the bottling plant promptly slashed the workers' wages: experienced workers went from earning $380 a month to $130.

At first, Coke said they weren't responsible for the behaviour of their subcontractors – even though they own a controlling share in this bottling company. Then they said "we take accusations regarding labour rights violations seriously". But in Carepa, Thomas found that "to this day, the Coca-Cola Company has not investigated the alleged links of Colombian bottling plant managers with the paramilitaries, despite a man being shot dead under their logo". Still the death-threats continue, pledging anyone "bad-mouthing the Coca-Cola Corporation... will be dealt with as they prefer: death, torture, cut into pieces, coup de grace. No more protests!"

This is not a lone horror-story. Thomas found children working for Coke contractors in El Salvador, and workers in Turkey beaten for trying to join a union. But the most striking story is from Plachimada, a village in Kerala, India. In the 1990s Coke opened a plant and began pumping half a million litres a day out of the underground aquifer. Suddenly the water in Plachimada's wells turned bad. A lab report for the BBC found it was now "so acidic it would burn up your insides. Clothes could tear in such water, food will rot, crops will wither". The village's children had to stop going to school and spend all day fetching water from far away.

As compensation, Coke's Indian subsidiary gave the local villagers their left-over industrial sludge to use as fertiliser. Incredibly, another test by the BBC found the "fertilizer" was filled with poisons. The doctors who examined it warned it could cause kidney failure or severe mental disability. Responding to this study, Sunil Gupta, Coca-Cola India's vice-president, said: "It's good for them because they are poor."

Yes, it will be annoying for me not to have my favourite drinks. But it's considerably more annoying to watch your children die of typhoid while your fresh water is being shipped off for the rich to quaff, or to be shot in the face for running a trade union. In 2009, I don't want to drink oil, or blood.