What's your question? Ask

This is not going to be a set amount. It will fluctuate based on the temperature and humidity of the environment. Generally, plants that like to remain moist will require the soil to dry out, ONLY, within the first half inch.

The point of spent coffee grounds will be to loosen up the soil. They will be void of nutrients until they are broken down by microbes. These plants are invasive, so adding much extra nutrients won't be necessary. However, used coffee grounds will provide grit and looseness to the soil.

https://www.gardeningknowhow.com/plant-problems/weeds/water-spinach-control.htm

https://www.gardeningknowhow.com/composting/ingredients/coffee-grounds-gardening.htm