"Creating" a ground pin for my laptop
Solving EMI problems can be tricky. The first thing would be to find out the source of the noise. Is it coming from the arudino or external to the arudino? Once you find out where it's coming from you can take steps to isolate the noise. 

Noise is usually conducted along cables, or radiated (like radio waves). The ideal sensor setup is shown below with shielding to stop radiated noise coming from other sources.



Source: https://www.electronic.nu/2016/05/30/shielded-cables-their-role-in-reducing-emi-susceptibilty-and-emissions/

If the noise is conducted, usually a ferrite to block noise from coming up the cable is best. 

The change in noise might also be caused by the way your device behaves, not from grounding (sometimes connecting a usb device turns whatever is on the end of the cable in to an antenna\radiator). 

If you have an oscilloscope, you could use it to probe the source of the noise (like on the ADC pins from the sensor, or the sensor itself) and find the frequencies of the noise source. Once you have found the frequency you could look at other noise sources like clocks or processors and try an isolate them from the sensor.