Money that, alone, would not be able to purchase something at a store or event. However, is used when a friend barely doesn't have enough money and needs those few extra dollars, or cent, to buy that clothing item or food that they've been looking at.
Support money can be completely worthless when you're shopping alone, but when it's you and your group of buds at the baseball/football/basketball/hockey game, it can really come through and nab you that extra set of nachos.
There's four friends at a football game: Anthony, Bill, Chris, and Derrick. Anthony and Derrick both buy something for themselves at the concession stand, but Chris cannot as he only has 76 cents, and Bill only has $3, which although is enough for a small popcorn, he is just under the price of the extra-large popcorn that he wants--$3.75. So Chris, with his support money, hands Bill the 76 cents, and Bill gets his extra-large popcorn. Both Bill and Chris share the popcorn, satisfied.