Brewing your cannabis will lead to a disgusting liquid, but nothing else. You'll feel bad but it will have no effects of cannabis because there will be zero THC. THC binds to fat so you have to add butter or oil to the water.
Yeah, which is why I question their results for cannabis: "Cannabis aqueous extract was prepared by first blending the dried leaves, and then blending the dried leaves in fine powder using a dry blender. The fine powder was thereafter soaked in water for about 12 h and filtered; the substrate was evaporated to dryness, weighed, and then prepared into the mixture of suitable concentrations for the various animal groups".
They also don't appear to have tested this solution for levels of THC, CBD, or anything else. Seems like a pretty poorly designed study. I'm somewhat surprised it even got published.
Look up "green dragon", it takes ~1 month to make and ends up turning a very pretty florescent green. A single shot gloss of the stuff is very strong, and two shots would be intense even for someone with a high familiarity / tolerance to cannabis.
Accidentally smoking your coffee and brewing your cannabis will make for a rough day I imagine