Often, incredibly popular and successful products turn out to be fads, with an almost irrational enthusiasm quickly transforming into disinterest. Investors who buy into companies with products that rapidly rise in popularity are always taking the risk that those products crash and burn with equal vigor.

Of course, fads are much easier to detect in hindsight. Remember Beanie Babies? Or the proliferation of cupcake stores in recent years? Predicting which currently popular products will turn out to be a short-lived craze is much harder, but that hasn't stopped these Foolish contributors from taking a swing.

Here's their takes on why SodaStream (NASDAQ:SODA)Keurig's (NASDAQ:GMCR) K-Cups, and free-to-play games from companies like Zynga (NASDAQ:ZNGA) and Glu Mobile (NASDAQ:GLUU) could end up being fads.

Andres Cardenal: Home soda looked like a promising trend a couple of years ago, especially in some European countries. SodaStream is a pioneer in home carbonation systems. The company sells the machines, the gas refills, and the flavors to make home sodas and sparkling water. As the company was rapidly expanding into the U.S., SodaStream looked like a promising growth stock offering exciting opportunities.

Sodastream

Source: SodaStream

However, sales have been quite disappointing during the last two years, and investors in SodaStream are clearly being hurt by the company's lackluster financial performance. SodaStream stock was trading in the neighborhood of $72 in June of 2013, and it has now fallen to around $14.50 per share.

Financial performance during the second quarter of 2015 doesn't provide much reason for hope. SodaStream's revenues declined by a worrisome 28% year over year, to $101.7 million, and the decline was pervasive across the company's different geographical regions.

The company is trying to reposition itself with new marketing campaigns focusing on the health benefits of its products. Consumers around the world are increasingly health conscious, but they don't seem to believe that making soda or carbonated water at home is the most practical and convenient choice. The way things are going, it looks like home carbonation will continue losing fizz in the coming years.

Tim Green: The incredible success of Keurig's single-serve K-Cup coffee makers seems to be hitting a wall. Sales of the machines are falling off a cliff, and even sales of the K-Cups themselves, where Keurig makes most of its money, have started to decline. A major misstep with the Keurig 2.0 coffee system, which only worked with Keurig-approved K-Cups, has seriously tarnished the brand.

The problem with Keurig's coffee machines, however, run deeper. K-Cups have never really made all that much sense, and I'm honestly shocked that they ever became popular. The inventor of the K-Cup, in an article from The Atlantic, said:

I don't have one. They're kind of expensive to use. Plus it's not like drip coffee is tough to make.

Keurig

Source: Keurig.

Beyond K-Cups being far more expensive than simply buying ground coffee, they're an environmental disaster. Keurig's K-Cups are recyclable only if disassembled, meaning that the vast majority of users will simply throw them away. Keurig plans to introduce fully recyclable K-Cups by 2020, but that's still a long way off.

Keurig's K-Cups, while still very popular despite slumping sales, have all the makings of a fad. Originally drawn in by the convenience over traditional drip coffee makers, the high cost and environmental issues seem to now be driving people away -- or at least driving them to lower-cost competitors now that Keurig's K-Cup patents have expired. While K-Cups are in no danger of completely disappearing any time soon, Keurig's cash cow appears to be vanishing. 

Steve Symington: I think the current "freemium" video game trend looks like a massive fad -- at least in its current state -- when game developers make their wares free to play, then monetize them through either advertisements or tempting in-app game purchases. Specifically, I'm concerned that, from an investment standpoint, the freemium model simply isn't sustainable on its own.

Words With Friends

Source: Zynga

For example, consider free-to-play game giants Zynga (of Farmville and Words with Friends fame) and Glu Mobile (creator of Kim Kardashian: Hollywood and Racing Rivals), both of which have struggled to achieve sustained profitability despite a solid slate of massive hit games. In fact, while Zynga is working hard to increase and monetize its mobile base -- bookings from which represented two-thirds of its total last quarter -- it still hasn't fully recovered since overall bookings peaked in 2012.

And though Glu Mobile saw impressive 64% year-over-year revenue growth last quarter, the stock got crushed after delayed releases of several titles resulted in a soft outlook for the year. That doesn't preclude Glu Mobile from achieving stronger performance when those games are ultimately released. But it does underscore the huge challenge these game makers must tackle to consistently encourage the casual gaming crowd to keep dedicating their time and opening their wallets.

I'm convinced that gaming trends favor more attractive options in paid titles -- even if for a few dollars -- or monthly streaming subscription services such as those offered by GameFly. Both provide access to a library of console-less, cloud-based games at an affordable cost, and could prove solid alternatives to the relative inconvenience of ads or in-app purchases. 

That's not to say freemium gaming will go away in the near future. But over the long term, if it proves unsustainable from a financial standpoint, these kinds of games will inevitably command continually decreasing attention from developers.

Andrés Cardenal has no position in any stocks mentioned. Steve Symington has no position in any stocks mentioned. Timothy Green has no position in any stocks mentioned. The Motley Fool owns shares of SodaStream. The Motley Fool recommends Keurig Green Mountain. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.