Cadbury Schweppes shares have risen 10% after a leading US businessman bought a stake in the confectionary and drinks giant, sparking takeover speculation.
Snapple is one of Cadbury's best-performing brands
Nelson Peltz, who owned the Snapple fruit drinks firm before selling it to Cadbury for £749m in 2000, has bought a 3% stake in the British firm.
Cadbury suffered a series of setbacks last year including a salmonella outbreak at one of its UK plants.
It had to take a million chocolate bars off its shelves, costing it £30m.
In Tuesday trading in London, Cadbury shares closed up 57 pence, or 10.5%, at 602p.
Cadbury confirmed that Mr Peltz and a number of his associates had bought 62 million shares in the firm, equivalent to 2.9% of its total equity.
Mr Peltz hit the headlines last year when he bought a stake in US food giant Heinz and sought changes to the company's board and strategy.
Analysts said Mr Peltz could possibly be planning similar action at Cadbury.
"He has considerable knowledge in the North American beverage market and clearly sees value in the company," David Lang, an analyst with stockbrokers Investec, said.
Cadbury's drinks brands include 7 Up and Dr Pepper while its chocolate range includes well-known bars such as Flake, Crunchie and Wispa.