In Ocean Beach, there is a multi-storey car park to the north of the Pole Position Club. On the top level is a parked Stallion. Enter it, and the "Cone Crazy" side-mission is activated.
You have to collect five checkpoints in the time limit without breaking any of the cones. Each checkpoint will credit you with 12 seconds of time, and are located in the midst of the cones. If you even break one cone, you will fail the side-mission.
You can easily line yourself up to collect the checkpoints, so wasting a few seconds to gather more is good. Plus, the cones take more than a nudge to break, so if you are cautious, you shouldn't have a problem concerning breaking the cones.
Your reward for completion is $200. If you retry, you will have to beat your best time, and your reward will double each time. You need only beat this once for 100% completion, however.