Why would Campbell want to buy UB, or SAB Miller go for Foster’s, ask Adam Leyland, Anna-Marie Julyan and Hannah Stodell

Some deals make sense. You can see why Kraft wanted Cadbury, or why InBev wanted Anheuser-Busch.

The rationale has just two permutations: either to grow the top line through a better route to market; or to use cost synergies to boost the bottom line. Or a bit of both.

But other deals are harder to fathom, and the latest rumours count among them. They concern Campbell's, the US soup and cookies player; and SAB Miller, the UK-listed South African/American brewing giant. And the targets are, reportedly, United Biscuits (rsp: £2bn) and the beer-making arm of Foster's Breweries (rsp: £7bn).

The rationale for Campbell's acquisition of UB, according to The Sunday Times report, is to sell off the bagged snacks to a rival, and keep the complementary biscuits ops, including McVitie's Digestive.

What makes the Campbell's acquisition so unlikely, however, is the fact it exited the UK in 2006, citing low growth and intense competition. Though deals are now better value aided by the pound's 16% deterioration versus the US dollar [FairFX] competition is, if anything, even more fierce, and growth lower.

Experts also see no obvious ­synergies in launching Pepperidge Farm cookies here.

"What they would be buying is scale, must-stock brands and an almost unassailable presence in the UK," says one dealmaker.

"It's a surprising development, but there appears to have been a change of strategy," adds another.

The Foster's deal is equally curious. After The Sunday Times broke the story, Foster's share price rose 8% sparking a price query from the Australian Securities Exchange.

Foster's Group effectively put the business up for sale in May when it announced plans to split the beer-making arm, Carlton & United Breweries, from its ailing wine businesses next year. And the true picture of Foster's finances was revealed last week when it posted an annual net loss of $464.4m, stemming from the earlier $1.3bn writedown of its wine arm. Earnings in the recently rebranded Treasury Wine Estates fell 27% to $221.3m while beer business earnings were up 5% to $904m.

But why would SAB Miller want in? A deal would add to the frenzy of consolidation in recent years that created ABInBev and saw Heineken snap up S&N in 2008 and Mexico's Femsa earlier this year.

And, as rivals pay off debts from recent deals, SAB Miller has money to burn. "It wanted Femsa, but wasn't prepared to pay 11.4 x EBITDA," says Absa Investment analyst Chris Gilmour.

As one half of a duopoly with Kirin-owned brewer Lion Nathan in Australia, however, and as owners of Australia's best-selling Victoria Bitter, CUB has a very high operating profit margin of about 35%.

"The duopoly means even though Foster's market share in Australia is diminishing, its margin stays high," adds Gilmour. "Who cares with that kind of margin if there are no great growth in volume?"

But with Foster's rights in so many key markets accounted for (Heineken owns the rights in the UK and Europe, for example; while SAB Miller licenses them in the US), it's hard to see where growth could come from.

Some have suggested a Foster's buyout could help SAB untap greater growth in Asia, lucrative in terms of volume prospects. But SAB Miller already owns the Foster's brand in India and is the sub-continent's second-biggest brewer. And in China SAB dominates with Snow, the world's ­biggest-selling beer.

"Foster's offers little growth in sales or profits, and has no obvious value from an international brand perspective as the Foster's licence has been sold to a variety of ­parties," says Investec Securities ­analyst Anthony Geard.

A buyout would also dilute SAB's growth profile, already looking diminished as Central and Eastern Europeans continue ­trading down into cheaper spirits, adds Geard.

So, a good call? We don't get it.