Mathur was a Wharton student who had taken social entrepreneurship courses.
They thought about the one billion people worldwide without access to clean drinking water.
They thought about the high use of bottled water in the United States, despite the easy access that most have to perfectly good tap water.
By 4 a.m., they knew what they would do.
They would manufacture a reusable, filtering water bottle - a more sustainable alternative to single-use bottles. And they would use the proceeds to bring clean drinking water to areas that don't have it.
"We looked at each other and said, 'You know what, this has serious potential,' " Parekh recalled.
Sure enough, everything began to click. They were semifinalists in the computer-maker's competition. They got accepted into a Penn business-incubator program.
The job market didn't look so hot anyway, so they formed their own company, Hydros Bottle L.L.C., and waded in.
Half a world away, Winston Ibrahim was visiting a university in Israel with a strong entrepreneurship program. The Philadelphia investment banker and 2009 graduate of Johns Hopkins University was impressed with the kinds of projects those students were doing. "That kind of planted a bug," he said.
Back home three weeks later, he bumped into Parekh and Mathur. Not long afterward, the Ibrahim Family Foundation, begun by his father - S.A. Ibrahim, CEO of Radian Group Inc., a global credit risk management company in Philadelphia - provided seed money.
The first bottle, which began as a sketch on the back of a piece of paper, came out early in 2010. Bottles were in Whole Foods by that July.
A newer version - with a side fill, straw attachment, and carrying loop - is due next month.
The components are manufactured in Illinois, northern New Jersey, and good old Northeast Philadelphia.
The carbon filter reduces chlorine and chloramines - both disinfectants that many find have an unpleasant taste or odor - and particulates.