Regular pilots wear a ‘G’ suit to help minimize the effects of high Gs. The Thunderbird pilots do not wear G suits because they fly so close to each other they are afraid if the suit suddenly inflated it might push them into another aircraft.
Takes amazingly fit people to sustain such high Gs without a suit. Sometimes it is a little too much even for them.
https://www.youtube.com/watch?v=mbr8KL90aa8
Almost any pilot with or without a G suits will start showing the effects of G-LOC at 8+ Gs in a very short time. Survival of that type of maneuvering relies as much on muscle memory and rote action as much as ground clearance and precision of maneuvering.
Yep - even a seemingly insignificant sugar spike or drop can make a huge difference when under maximum physical stress...I’d wager their diets are closely monitored to try to have them at peak when performing.