The following is a list of popular brand-names and companies in the GTA universe it may be useful to know.
Original list compiled by @Silverfish in 2019 but never completed or expanded upon. I'll be doing that!
I hope this is a useful resource for anyone. Good for figuring out what your character drinks or smokes.
ALCOHOL
CIGARETTES & TOBACCO
SNACKS & SOFT DRINKS
CELL PHONES
WEAPON MANUFACTURERS
FASHION BRANDS
AUTO MANUFACTURERS