Ever tried to drink from a bottle whilst whipping down singletrack or hammering up a climb? Camelbaks are easier and you don’t have to pit. And you don’t take 2kg of water for a 90 min race.
Anyway, re red bull – it’s not just caffeine, it contains no more caffeine than a can of coke (according to the red bull lass I talked to, 35mg caffeine apparently). It does contain taurine which is an amino acid, linked to tiredness.
From my own experience it is the only thing that really perks me up and makes me feel normal and not tired. Coffee just makes me feel tired and scrambled, then a bit sick (even though I love it) and gives me palpitations if I drink enough.
On the subject of drinking it before a ride – it probably brought your blood sugar levels up. You should be taking carbs throughout your ride if you want to have a decent one and not die.