Nothing beats having your fuel right under your face on a long ride, and Bontrager’s top-tube larder does the job nicely.
It’s a small boat-shaped tub made out of the stuff they use for sunglass cases, and big enough for a couple of energy bars, gels, or even a couple of CO2 cartridges and a minitool.
A teardrop stretch mesh cover hooks over a short stub at the back to stop stuff flying out. You do have to fetch stuff out back to front though. Twin straps with rubberised backing grip the top tube, while the short bungee loop goes round the stem or seatpost. You’ll have to pull the stem off to fit it if you’re using tri-bars, but it works fine.