To increase the speed of the particles in the container, the best option would be:
keeping the pressure constant and increasing the temperature.
Increasing the temperature of the particles will increase their kinetic energy, thereby increasing their speed. Keeping the pressure constant while raising the temperature means that pressure-volume work can accommodate the increase in energy without the system becoming unstable.
The other options would either decrease the speed of the particles (e.g., cooling) or not significantly affect their speed (changing from light to heavy particles at constant volume).