I've written a short film and hope to submit it to a few short film festivals. However, I mention a certain popular soft drink throughout (positively I might add) and want to know if this is allowed? I also plan to have one character drinking it in the final version. Is this ok too?
Thanks
You are free to mention R Whites, Irn Bru or any soft drink. Just as long as you don't refer to Googling the internet or Hoovering the carpet, that's illegal. 
Is the actual product's brand name integral to the plot?
Is it Duff beer? Buckfasts gets mentioned all the time in Rab and Still Game a bit.
Surely the actual brand doesn't need to be mentioned. Can't you make one up?