Why Red Fanta?
Because the spirits (Phra phum) prefer it. Because it is a favourite drink of the King of Thailand. In truth nobody really seems to have a definitive answer. People I have spoken to who claim to have seen the spirits say that are red in colour so this may be an explanation. Mind you they may have only got that way from from drinking too much Red Fanta (Nam Dang - Red Water). What they drank before Red Fanta arrived on the Thai market is anybody's guess.
The spirits are not so much a Buddhist thing so much as an animist belief in spirits which goes back to before Buddha was born. Spirits are everywhere. They need to be appeased to be kept happy or they will disrupt your house and business. Most houses and businesses will have spirit houses outside, maybe two or three. Usually in a garden or sometimes on a roof. Every bar or restaurant will have a shelf on which offerings are placed with frequency. Accident black spots too will sometimes have several spirit houses.
Spirit House with Red Fanta
Milk and Water too
Of course the spirits do drink other things. Milk and water are favourites too and any Bar spirits will get their share of the spirits being served there.
A Milk Treat too but don't forget the Red Fanta
A curious thing
It was a tradition in our house on Christmas Eve to leave a glass of brandy and a slice of cake for the man in red and a carrot for the reindeer. The brandy was always drunk, the cake partially eaten and the carrot nibbled. Of course I learned long ago that it was my parents who did the deed and I carried on the tradition with my own children.
Why do I mention this?
It is because I have yet to find an explanation as to who drinks the Red Fanta. Evaporation, I hear you say. Not so. There is no way that that amount of Red Fanta will evaporate whether indoors or outdoors. I have even done my own little tests. A bottle in a locked bar can lose a third overnight.
House spirits, tree spirits, water spirits, bar spirits, zoo spirits. They all like Red Fanta. You can believe it or not. As long as we keep them happy.