How do you get money fast on sonic adventure 2 battle

one of these three levels city escape (sonics first) or the kart levels


the other way is with a glitch that i could never get to work but aparently does.

buy an expensive object and then sell it again. while the CHING-CHING is going you turn off your console. this should give you the money and you keep the item. But remember this has never worked for me and it is high risk as you must get it to work 4 times before you start to make profit.