My brother has been tricked into drinking urine at work...is this assault?

[disgustedperson]

The disgusting little bartenders thought it would be a good wheeze to trick him.....he's now unsure what to do....I think he should inform his boss and have the dirty little crap heads sacked...or the police....there's no proof though....the glass has been done away with.

What can he do I am livid on his behalf and am very close to going in there and banging their heads together...

Oh how horrible :-(
If it's any consolation to your brotherm urine is sterile but still an utterly vile thing to do. Does his workplace have a policy on bullying and harrassment? I would certainly complain to his line manager (your brother, not you!) and take it from there.

If you work on the assumption that urine is a noxious substance which may cause harm (think infected pee) and that it was administered maliciously with intent to do harm or cause distress then I think it is assault. Think poisoning someone with screen wash (ann summers boss!!) screen wash is not poisonous, was hidden in food with intent to cause distress and the perpetrator is behind bars! Ann Summers had proof though
Your B would be in difficulties if there is no proof, so your best bet is the management route.
Tell him to laugh it off, be friendly, make sandwiches for them and spit in every one. Childish but it works.