Here's a couple of things I do and find effective when I'm Sonic fighting Snake:
1) Pick up grenades and toss them back. If you're bold enough to do this and do this well, Snake will think twice about tossing those.
2) If Snake uses the Cypher from below the stage, use fair to rack up damage.
3) If Snake uses the Cypher from above the stage, spring up and delay your attack. You might have to pay a price first to see what your particular Snake will do against you, as some will airdodge (as you will can punish their unnecessary airdodge because you didn't attack), while some will attack (then you know that the Snake is aggressive in the air and you either don't attack or find a mindgame to counter that).
4) If you play a Snake that loves dash attack usmashes, it can be punished with a quick grab if they don't slide far enough... IF they don't slide far enough. Otherwise, let it go and try another set up.
5) Misslies are TOOOOO EASY TO PUNISH with the speed of Sonic. If for some reason Snake fires a missile without having an explosive defense in front of him, do something about it.
6) Spot dodge his tilts, then counter with a tilt (not a smash, a tilt).
7) Sonic usmash beats Snake's fsmash, as they both have pre-lag. Of course, if you're that late with it, you'll get hit anyway. Hyphen Smash him then.
1- Be wary of Snake's grenades if he only has one out. He can take out a second one and use it to force you to drop it, which can mean that if he drops right before you attack again, instead of throwing it, it will drop and when you press [A], you'll pick it up again or attack it and make it explode. If anything, abuse his 2nd grenade, or if you pick up the first one, be wary of the Snake's actions.
2- If Snake is below the stage, I tend to late-N-air (if he's far) or drop behind and go for a stage spike.
On another note, it's possible to grab Snake out of cypher before he even airdodges, if you can grab him as his head is passing the edge.
3- If the Snake is above the stage, like, really high, you have to be predictive, as previously stated.
What you can do sometimes is move ahead of him and try to use that amazing Spring>U-air-priority to catch him on his way down, but time it so you hit towards the end of the rise. Most people will try to outprioritize you, and may get caught, but if they're smart and airdodge, then at least you can try catching him again.
If you can predict about 3 seconds ahead, do a reverse spring>lagless D-air landing, then jump on the grounded spring. From here, you can try doing a rising ASC (remember ASC has high knockback, and it can/will kill from that height at over 100%) or try to catch him with a side-B, and out of either one, go into a U-air>spring U-air combo.
4- If you're close to Snake and he's doing the mortar slide, you can turn around, shield his initial mortar, and grab him as he passes you. I believe F-tilt works as well. If you're out of range of his initial hit, you can attack him out of it with any attack.
6- Personally I shield grab tilts. But be wary of rolling behind Snake. They tend to prepare for those reactions.
