That income could vanish quickly if Monster were sold to a strategic buyer that decided to take away Coca-Cola's piece of the Monster distribution. Take Anheuser Busch InBev. While state laws often prohibit beer companies from owning their own distributors, several partner distributors of AB InBev currently work with Monster and would surely enjoy the added volume. AB InBev declined to comment.
Similarly, PepsiCo could likely find big synergies if it acquired Monster and added the energy drink company's products to its normal distribution routes. While U.S. beverages are less important to PepsiCo than Coca-Cola in terms of revenue and profit, the two companies face similar challenges in the domestic soda market. PepsiCo declined to comment to CNBC, but the company has said it is focused on smaller tuck-in acquisitions.
Read MoreInvestor: Coca-Cola 'hijacking' shareholder buyback
If Monster were gobbled up by a rival, the pressure on Coca-Cola to meet its long-term targets would likely intensify. The company has a target of doubling its 2010 revenue by 2020—including any acquisitions—which implies a roughly 7 percent annual growth rate. Unfortunately, that has proven a tough pace to achieve. Coca-Cola's company-wide organic revenue grew 6 percent in 2012 and 3 percent in 2013.
A natural solution would be for Coca-Cola to acquire Monster. The deal looks attractive both because of Monster's own sales growth as well as the opportunity to distribute its products to more locations, many of which Coca-Cola already serves. Indeed, a deal would add an estimated 4 percent to company-wide revenue in 2015 and 10 percent to operating profit, Swartzberg said.
Of course, valuation is often an issue with high-growth companies, particularly in recent months. But Monster trades at an enterprise value, adjusted for cash, of 12.9 times 2015 consensus earnings before interest, taxes, depreciation and amortization. That's less than Coca-Cola's multiple of 13.3 times, despite the beverage giant's weak stock performance over the last couple of years.
Read MoreBig dividend staple stocks show their dark side
Monster shares look like a reasonable deal considering its growth outlook. While Coca-Cola's U.S. carbonated-drink unit volume declined 2.2 percent in 2013, Monster's rose by 7.7 percent, according to Beverage Digest.