I typed up some anti-Blanka:
Beat the Slide Punch
Standing short beats not only the slide punch but also horizontal balls and Blanka’s super. One of the sweetest things Guile can do is jab sonic -> standing short. If Blanka tries to slide under the sonic at max-range your short will hit him into it for a 2 hit combo.
Try to catch him as he goes into the punch. Especially good if Blanka tries two slide punches in a row – hit him with roundhouse in between. Blanka can beat Guile’s standing roundhouse with his standing jab but if he’s doing those jabs you can hit him with an old fashioned crouching forward.
Mix these in with the jab sonic booms sometimes to try to catch him flinching.
No-charge Air Defense (Standard)
Any given option can be beat, so good anti-air is a matter of knowing the proper spacing and reading your opponent.
Loses to a late Blanka jump fierce. You can also do the crouching forward a little late looking for a blocked hit. If Blanka is really sneaky he could forward hop over that one but you should have a Flash Kick charged by then so…
Vertical jump roundhouse / climbing jump fierce
If you’re backed into the corner and you get beat air-to-air by a Blanka jump jab, note that you’re vulnerable to his fierce ball trickery so be careful.
This usually loses to Blanka’s jump short but that ain’t the end of the world. Do it early such that Blanka hits you high, and you can do a defensive two-way mix-up on the back end: sac-throw or Flash Kick. Crouching fierce a little later if you’re trying to trade.
No-charge Air Defense (Non-standard)
At long range this is not unlike Sagat’s standing fierce. Do it as late as possible to try to trade or beat Blanka’s jumping jab/jumping roundhouse.
Far standing strong
Neutral or back+medium kick Sobat
Standing short (!?)
All weird shit that you see Muteki doing against Blanka players sometimes.
Blanka is a huge target for an ambiguous jump short -> crouching strong -> (hit confirm) flash kick. If your opponent has a reliable reversal vertical ball this doesn’t mean much but…
Whiff -> Throw Trickery
Up close, joystick plus roundhouse (the upside down kick) and joystick plus medium kick (sobat) both miss. Whiff the kick and throw the beast.