Jase, not entirely sure on the official rules for this, but here goes….
For the Eastern League, one is able to carry bottles in any race.
However, only in certain races is one allowed to be handed up a bottle from spectators/helpers. One situation in which this is allowed is when the temperature is high, and this happened last week in our race at 23 deg C.
Bike swapping is done if one bike is particularly muddy or there has been a mechanical/puncture. For those lucky enough to have one, the helper will clean or fix the other bike. I have a couple of bikes, but the backup one rides like a dog, so I only swap to that reluctantly.