The Calcalist financial newspaper in Israel reported earlier Thursday that PepsiCo is in talks to buy the company, whose machines make carbonated drinks from tap water, for $2 billion.
When asked via email whether there was any truth to the report about Pepsi buying SodaStream, Nooyi told CNBC the report was "totally and completely untrue."
SodaStream, which also makes flavors, carbon dioxide refills and re-usable bottles, was listed on Nasdaq in 2010 and has a market valuation of $1.4 billion.
Estimates are that PepsiCo is willing to go even higher than $2 billion and might agree to pay as much as $95 per share, Calcalist said. SodaStream's shares closed at $69.35 on Wednesday.
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PepsiCo has already made an offer to buy SodaStream through Goldman Sachs, according to the report.
Officials at SodaStream were not immediately available for comment.
The paper reported that PepsiCo is interested in SodaStream's potential to expand in the United States after its U.S. sales doubled in 2012.
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Calcalist also said SodaStream is checking its options for a deal with Coca-Cola before moving into advanced negotiations with PepsiCo.
Global sales at SodaStream, which sells at upscale department stores such as Harrods as well as at budget chains like U.S. group Target Corp, have risen more than three-fold since 2009. The group booked sales of over $436 million last year, with net profit up 18 percent to $44 million.
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—By CNBC.com With Reuters; Becky Quick contributed to this report.