I need a quick plan to burn fat?

I wanna look good before I visit my hometown, I don't really care about the number of weight it's just the fat, I don't have that much but i want it gone. Most problem areas are around my legs hips and under arms that I want gone, My body has kind of been through hell lately since I was just released from rehab, I was skinny while on drugs (Crystal meth,Heroin) But gained a little bit of weight in the place. I have 21 days to burn the fat. any suggestions that will be good?