The founders of Pyknic were among the most promising 25 businesses run by entrepreneurs under age 25. readers voted them among the top five winners. The five winners that garnered the biggest shares of more than 13,000 votes cast are all either profitable or cash-flow positive.

College friends Andrew Marshall and Stephen Thompson started Pyknic in 2006 by selling a first run of 200 T-shirts they had decorated by hand with Sharpie markers to their classmates at DeSales University in Center Valley, Pa. Today they’re projecting $500,000 in sales for 2010, double what they recorded last year.

Andrew Marshall in a statement to businessweek said “We funded everything ourselves. We didn’t have that much money to begin with.”

Andrew Marshall and Stephen Thompson run the operation on their own out of a warehouse in Robbinsville, N.J. The T-shirts, which retail for about $20, are conceived with food themes and rendered in cartoonish fashion. The shirts are printed by contract printers in the U.S. and China and sold online.