In an instance where you're using just a PV panel to charge one unmodified phone or laptop, then you can't. As I mentioned, with a fixed 5V output (or whatever voltage your laptop uses), you don't have the option of doing any kind of current control, therefore MPPT is not possible.
But if you were to attach a battery pack to the PV cell to buffer the energy, then you would be able to use MPPT. Alternatively if somehow you were able to access your phone/laptop's charge controller to allow variable charge current, then MPPT could be implemented.
Many smartphones for example can select between two or three charge rates depending on whether they're connected to a USB 2.0 port, wall wart, or something proprietary, one way of "hacking it" would be to have the PV panel toggle the smartphone between these three charge rates, to achieve some approximation of MPPT.
If you're interested in MPPT, then probably attaching a battery pack to the PV cell would be the wisest choice.