Few things translate perfectly from one language to another. That's why we often have to reword or entirely rewrite when translating. It's also why major companies work closely with native speakers for localization. A badly worded product or ad could turn the company into a laughingstock as these examples show.
Pepsi the reanimator
There's a popular urban legend that Pepsi's slogan "Come alive with the Pepsi generation" was mistranslated into Chinese as "Pepsi brings your dead ancestors back to life."
While I couldn't find any solid sources for this (such as Chinese articles about it, which I surely would've found), it sheds light on the fact that Chinese characters are ideograms, so while translating product names into Chinese, companies have to be careful. Coca-Cola's original name in Chinese was ke-kou-ke-la, which literally means "Bite the wax tadpole" or "Female horse stuffed with wax." The company ended up choosing characters that read, "Brings joy to the mouth."
Charlie bit my finger off
KFC also ran into some trouble in China with its slogan, "Finger lickin' good." Apparently the way it was worded, Chinese consumers misunderstood the slogan to mean, "Eat your fingers off." KFC changed the slogan and now it's 900 stores strong in the Middle Kingdom. For the record, the colloquialism hasn't translated well into German, Thai or some other languages as well.
The Spanish market is important for American businesses and quite a few of them have made the Spanish speaking world laugh at their horrible translations. Coors originally translated its slogan "Turn it loose" directly into Spanish, in effect encouraging Spanish speaking consumers to suffer from diarrhea.
The car that didn't go
Car companies have made some fairly famous mistakes in naming their products for Latin America. Probably the most famous is Chevrolet's Nova, which in Spanish sounds like no va, or "Doesn't go." This Spanish 101 mistake led the company to pull the car off the market due to its lack of sales.
Another example is the Mitsubishi Pajero, whose name is a slang term for a man's private part. It was later changed to Montero for Spanish markets.
Likewise, American Motor Corporation's Matador didn't do well in Puerto Rico, where the name can mean 'killer.'
Pope the Spanish potato
A t-shirt manufacturer made an even simpler Spanish mistake that cost it big-time. It made t-shirts to commemorate the pope's visit which read la papa (the potato) instead of el papa (the pope).
For our last Spanish slip-up, you're surely familiar with the "Got Milk?" campaign. When translated directly into Spanish, it means, "Are you lactating?"
Tissues for whores
It must be tough for American companies to break into the markets of European countries. There are so many languages and so many opportunities for silly mistakes. American tissue brand Puffs discovered this the hard way. In German, "puff" is a slang term for whorehouse. In the U.K., it's close to "pouf," a derogatory term for homosexuals.
Cough cough drops
Vicks Cough Drops is another company that had to change its name or else face snickers in Germany. It changed its name to Wicks in Germany because "vicks" sounds a lot like a slang term for sexual penetration. Companies that use 'mist' in their names have to be careful in Germany as well, since the word sounds like a slang term for excrement. It makes Irish Mist or Mist Sticks sound like something else entirely.
The small car that didn't fit
The Honda Fit (U.S.) or Jazz (Europe) was originally called the Fitta but changed after it was discovered that this is a very unflattering slang term for female genitalia in Norway and Sweden. The name would've made the slogan, "Small on the outside but big on the inside" much funnier.
Will it suck?
English speaking companies aren't the only guilty parties. Scandinavian vacuum cleaner manufacturer Electrolux had to change its slogan "Nothing sucks like an Electrolux" before it could start selling on the American market.
The internet pecker
Japanese electronics manufacturer Panasonic must have been ecstatic when they got the license to use cartoon character Woody Woodpecker as the mascot and guide for their web browser. Luckily, someone stopped them before they launched the browser with its slogan, "Touch Woody – The Internet Pecker."
F*** the diet
German food brand Unilever last year unrolled a new ad campaign whose slogan is "F*** the Diet." I personally think that's awesome, but I can see how it would rub many English speakers (like most of them) the wrong way. However, it should be noted that the campaign is directed at German consumers, who are not so offended by f-bombs.