The paper shows its funding source The paper was published by authors from universities funded by government grants

The research leading to these results was funded by the European Union Seventh Framework Programme (FP7/2007-2013), under Grant 613960 (SMARTBEES) and by the Dipartimento diScienze AgroAlimentari, Ambientali e Animali, University of Udine, Italy.

Here another talking about the sugar water use and harm if you don't trust the first

The immune system is one of the animals’ most expensive physiological systems to maintain, especially when food is deficient in proteins [2,11,12], which is extremely frequent in commercially kept colonies, usually fed on sugar syrup

And for author information:

Funding

The study was supported by the Eastern Apicultural Society of North America (grant awarded to E.T.), and by the Ministry of Education, Science and Technological Development of the Republic of Serbia (Grant No III46002 awarded to the project led by Zoran Stanimirovic). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Acknowledgments

Authors are thankful to the beekeepers from West Serbia (Sjenica, Prijepolje, Tutin, Raška, Novi Pazar and Priboj) for allowing the access to their honey bee colonies

Conflicts of Interest

The authors declare no conflict of interest.

https://www.mdpi.com/2075-4450/11/5/266

getting off the internet and talking to some actual apiarists

Hopefully it’s easy enough to find the sources they’re relying on. If you don’t know apiarists you might have to burn a lotta gas or spam email some to talk to them.