These aren't sudsy days for PepsiCo (NASDAQ:PEP). The soda and salty-snacks giant is in a funk, but the stock is still trading closer to its highs than to its lows. 

Armed with a substantial yield and several brands topping $1 billion in annual sales, it's a popular investment. There are still some things that investors need to watch out for that could send the stock reeling. Let's check three of the things that could send PepsiCo stock lower. 

1. The strong dollar can hold back revenue
Like many global brands, PepsiCo is paying the price for the dollar's strengthening against most foreign currencies. Reported revenue has posted year-over-year declines in each of the past four quarters, according to S&P Capital IQ data. 

It's an illusion. PepsiCo's sales volume is improving at the local currency level, but things get wonky when weakening foreign sales get translated back into the U.S. dollar for financial reporting. Organic revenue actually rose by more than 7% in its most recent quarter, but it was reported as a 5% decline as a result of a 12% impact from adverse foreign currency moves. 

2. Dividend hikes can dry up
PepsiCo has come through with 43 consecutive years of dividend increases. That's an impressive streak, but with its yield now at 3% -- and earnings going the wrong way -- it's time to weigh the possibility that payout increases could be a thing of the past. 

Let's look at what PepsiCo earned in the past three years, the dividends it paid out, and how that breaks out in terms of payout ratios. 

 YearCore EPSDividendPayout Ratio
2013 $4.37 $2.27 52%
2014 $4.63 $2.62 57%
2015 (Estimated) $4.57 $2.81 62%

Source: PepsiCo press releases.

The increasing payout ratio means that more of PepsiCo's net income is going to justify its chunkier distributions. Dividends can't keep moving higher forever if PepsiCo's ability to meet those obligations diminishes. There's enough wiggle room for at least a few more year of payout hikes, but if earnings deteriorate through 2016 it will bring concerns for yield chasers that the streak will end sooner rather than later. 

3.Weak soda consumption trends can continue
PepsiCo is scoring meager gains in its beverage business, but soft drink consumption continues to decline. We've seen soda sales in North America decline through most of the past decade, and diet soda sales have fallen even harder in recent years.

PepsiCo still has Quaker oatmeal, Frito-Lay snacks, and Gatorade thirst quenchers, but it needs its flagship soda sales to reverse the problematic trend if it can't continue to expand it offerings.