Business travelers are a busy bunch, no doubt. Apparently they're so busy, in fact, that they can't keep their favorite restaurants, airlines, car rental companies and hotels straight.
Starbucks, Delta Air Lines, Avis, and Marriott had the largest percentage of receipts in their respective categories, according to new data from Certify, a travel and expense report management company. But Chick-fil-A, Southwest Airlines, Enterprise, and Residence Inn got the travelers' highest ratings.
Why the split?
Corporate policy, said Robert Neveu, president of Certify. Companies have preferred vendors, so employees often have to patronize businesses they don't love.
"It's bipolar if you will," he said. "Corporate policy says do one thing, but the users want to do something else."
(Read more: On jammed jets, travelers turn on one another)
According to the survey, business travelers in 2013 were most likely to spend $225 on a stay in a Marriott, grab a $10 breakfast at Starbucks, rent a car from Avis for $171 and fly to their next stop on Delta, spending $391.
Marriott took the top spot from Hilton, where travelers were spending an average of $271 in 2012. Delta was the most expensed airline for two years running, but travelers spent less in 2013: $391, down from $474. Starbucks also remained the most expensed in its category for two years, but business travelers spent $10 on average in 2013, up from $8 on average a year earlier.
"Starbucks continues to just kill it across the board," Neveu said.
Business travel continues to grow, according to the Global Business Travel Association. It expects U.S. spending on outbound international travel to grow to $36.7 billion in 2014, a 12.5 percent increase. Spending on domestic travel is expected to advance more slowly, just 6.6 percent, but it will continue to account for the lion's share of business travel spending at $289.8 billion.
As for individual items in business travel expense, flights are relatively big ticket, but meals accounted for almost a quarter of all business travel spending handled by Certify, beating out airlines.
(Read more: Pricey cocktails gaining traction at hotels)
The category accounting for the third largest share of travel and entertainment budgets? Miscellaneous. Corporate accountants, put on your detective hats.
—By CNBC's Kelley Holland. Follow her on Twitter @KKelleyHolland.