I'm training for a 100k road ride and want to buy suppliments to keep my blood sugar stable. Any suggestions?
Depends on if you are fuelled by carbohydrates or ketones, frankly.
Ketones you are heavy on the proteins and fats, with isotonic drinks (without sugar) to maintain your salt balance.
I can do around 55 miles/88k on coffee+double cream+salted butter.
As far as I know I am burning ketones which the liver produces from fats.
So the energy store is more or less bottomless, unlike carbohydrates.