'Touch grass' is not meant to be taken literally. Most broadly it means to go outside. It is an urge to go into the sunlight, breathe fresh air, be in nature. So, you can work in your garden, have a walk/run in the local park, ride a bicycle, walk/play with a pet, swim...

On the other hand, literally touching grass (sand and soil work equally good) is very healthful grounding technique where you discharge negative energy and recharge with positive energy. It is ideally done barefoot and before noon.