It's the pitchside bottle-throwing habit which drives some Premier League club doctors mad.
A player will catch one, drink from it and throw it back over the white line from where it will be placed back in the rack for anyone else to use — a ready-made means to transmit the viruses to which elite players can be particularly prone.
One doctor speaks of pushing to get name labels put on bottles to prevent a virus spreading in such an elementary way but it was a struggle. Players in prime physical fitness, playing elite football week-in week-out, think they're untouchable.