There's a bunch of inexact "scientific" articles from <1990 that will lead a lot of people to believe that feeding plants directly with glucose, sucrose, etc. will show them take it up and, consequently, take up nitrogen and other vital nutrients more effectively.
They aren't wrong, but they were wrong in that they didn't recognize the actual mechanism of action - what the plants actually use the sugars for and how the microbes and the enzymes those microbes produce directly impact plant function.
Plants also absorb food coloring through their roots. What significance should we designate for that?
I'm not an expert, so certainly don't take my word for it. But I'll be happy to link as much research as to numb your brain.
edit: It should also be noted that much of this is still in hypothesis. Whether or not the plants actually use added sugar that they can absorb for functions other than those of symbiosis is on the table.