That clip where Nole is eating somethng while holding up a towel is nothing, i really doubt a top tennis player would deliberately act so suspiciously during a live televised match in front of so many fans if in fact it was something dodgy he was taking.
I agree, especially as they know very well that the cameras are focussed on them all the time when they're sitting down at change of ends, sometimes embarrassingly so. I'm really not interested in watching players' scratching their noses or whatever.
Anyway at least he wasn't doing what male tennis players used to do behind their towels before "comfort breaks" were introduced, i.e. pee into empty drinks' bottles!
I do have sympathy for sportspeople in general though because some of them are so terrified of being accused of taking PEDs that they won't even take medication to help medical conditions such as asthma - the reason being that some perfectly legal drugs can undergo chemical changes in the body which can result in them showing up in urine samples as having an illicit content. I also seem to recall Andy being worried before RG (I think it was last year) because he had a skin infection which required treatment by antibiotics. Players though are under an obligation to check any kind of prescribed or over-the-counter medication out with the tournament doctor so that erroneous urine/blood test results can be avoided.