The fact that Altria (ex Philip Morris), a tobacco brand, made it to this list is telling IMO. There is no way that the cigarette packaging produces that much identifiable plastic trash.

My guess would be that in some countries, the stores provide disposable plastic bags with any purchase and that these bags include ads for tobacco brands. This study would associate the brand with the generation of trash while the trash should rather be associated with the store.

I'll personally classify this study as unreliable.