Back in the 60s, we raced in the pre-Gatorade days. I used to carry tea mixed with honey in my bottle on longer rides, water on shorter training days. We used old school metal bottles, and I had a double handle bar rack, one for water and one for tea and honey. On a longer rides it seemed lukewarm tea and honey worked better for me than luke warm water.
On shorter rides I used the second bottle cage to carry a spare tubular tire,