It's not "a few powerful sugar farmers" who benefit.
Sugar farmers are at the mercy of the transnational food processors and traders, just like the consumers are. The subsidies merely keep too many farmers from going out of business, and assure consumers that there is a plentiful supply of sugar.
Transnational food processors, such as Coca-Cola and Pepsico are the real beneficiaries, reducing the supply so they can profitably jack up the price and screw consumers worldwide.
Addendum: with dominant market share, economies of scale and brand name recognition, transnationals like Coca-Cola and Pepsico can afford to aborb and/or pass along these rising sugar prices to consumers. Their smaller competitors cannot endure rising commodity prices so readily. This is how monopolies and oligopolies exert and consolidate control over the market.