Pinkie has shown the ability to store items in her mane with seemingly limitless space, so it’s possible she already had all of those baking ingredients on her at the time. She has also been shown to be able to keep up with Rainbow Dash on hoof while Rainbow was actively trying to escape her. Rainbow never made a sonic rainboom, so let’s assume that she was flying at 90% of the speed of sound. During the scene where Rainbow was fleeing Pinkie, Pinkie somehow managed to always get to where Rainbow was going, before Rainbow got there. This means that Pinkie Pie is theoretically capable of running over 690 mph (~1110 km/h). It’s likely that Pinkie has always been able to do things this fast, but chooses not to for the sake of having while fun doing it.