So for whatever reason, you're looking for a secondary, but you're not sure who. If you are sure who, don't bother reading this guide. Otherwise, read on.
There are several reasons why you might want to find a secondary. I will list them here and give a description, along with suggestions on who to try. Keep in mind that this is a guideline, and you don't have to follow any of my advice; this is just to help you along if you're completely indecisive.
So now, the reasons.
I'm not winning enough.
Yeah, Sheik isn't high tier (maybe). Deal with it. Or don't. If this is seriously why you're looking for a secondary, consider finding a new main instead. You will find the most success with top tiers.
Suggestions: Meta Knight, Snake, Falco, Diddy Kong, King Dedede
I'm bored of only using Sheik.
Well, if this is the case, then only you can really decide on which character you actually want to mess around with. There's no particular motivation behind your choice, so your decision isn't exactly narrowed down any.
Suggestions: uhh... try Zelda? Or just go through the rest of the roster
I fear a character matchup.
Meta Knight
This is one of those matchups where you have to ask yourself if you really want to main Sheik or not. If you actually cannot handle playing Sheik against Meta Knight and are looking for a secondary, then this is problematic because Meta Knight will likely show up in at least 40% of your tournament matchups. Yeah, you'd be picking up a secondary that you use practically half the time.
Suggestions: Meta Knight, Snake, Wario, Diddy Kong, Marth, Pikachu, Ice Climbers
Ice Climbers
Sheik's most obviously bad matchup. Yes, she's got projectiles and can avoid getting grabbed... just like a whole lot of other characters. That doesn't exactly shift the matchup in her advantage when her actual options for disrupting the ICs are relatively minimal and she gets chaingrabbed by Popo alone. If you're actually planning on going all Sheik and braving this matchup, I salute your bravery, but wonder why you're reading this guide.
Suggestions: Zelda, Meta Knight, Snake, Wario, Zero Suit Samus, Peach, Mr. Game & Watch
Pikachu
Pikachu can chaingrab you if he lands a grab from like 0-15% or so. Deal with it.
Suggestions: Learning not to get grabbed at low %'s
Falco, Diddy Kong, Mr. Game & Watch
Uh... really? Do you seriously have that much of a problem with slightly disadvantageous matchups? Well, if you really feel the need to counterpick your way to a victory, and don't want to learn more than one other character...
Suggestions: Meta Knight, Snake, Falco, Diddy Kong, Mr. Game & Watch, Marth
I fear a stage.
Brinstar
This is one of those love-it-or-hate-it stages, based mostly on how comfortable you feel about moving around on a stage with acid, oddly placed side platforms, and uneven ground. If you've just had a bad experience on it, try first playing on it a bit more with Sheik before immediately looking for a secondary.
Suggestions: Meta Knight, Wario, Mr. Game & Watch, Pikachu, Donkey Kong
Frigate Orpheon
Okay, yeah, the right side is pretty scary for you. Another one of those stages I suggest actually practicing a bit on before you decide whether you actually hate it or not. Aside from the ledgeless right side during the initial form, this stage isn't actually terrible for Sheik.
Suggestions: Meta Knight, Mr. Game & Watch, Marth, Pikachu, R.O.B.
Jungle Japes
You really ought to ban this stage against Falco, you know. But if you didn't, and you get counterpicked to it, and your opponent is using Falco, then I guess you'll have to learn a secondary.
Suggestions: Snake, Falco, Diddy Kong, Wario, Mr. Game & Watch
Rainbow Cruise
Another one of those stages that you'll either be fine with or absolutely hate. In this case if you're having troubles with the stage you'll want to find a secondary that can better maneuver it.
Suggestions: Meta Knight, Mr. Game & Watch, King Dedede, R.O.B., Kirby
Final Destination, Battlefield, Smashville, Yoshi's Island, Lylat Cruise, Pokémon Stadium 1, Halberd
Dude. Dude. .... Really?
Suggestions: Finding a new main
If you have any other ideas or reasons to look for a secondary feel free to mention.
There are several reasons why you might want to find a secondary. I will list them here and give a description, along with suggestions on who to try. Keep in mind that this is a guideline, and you don't have to follow any of my advice; this is just to help you along if you're completely indecisive.
So now, the reasons.
I'm not winning enough.
Yeah, Sheik isn't high tier (maybe). Deal with it. Or don't. If this is seriously why you're looking for a secondary, consider finding a new main instead. You will find the most success with top tiers.
Suggestions: Meta Knight, Snake, Falco, Diddy Kong, King Dedede
I'm bored of only using Sheik.
Well, if this is the case, then only you can really decide on which character you actually want to mess around with. There's no particular motivation behind your choice, so your decision isn't exactly narrowed down any.
Suggestions: uhh... try Zelda? Or just go through the rest of the roster
I fear a character matchup.
Meta Knight
This is one of those matchups where you have to ask yourself if you really want to main Sheik or not. If you actually cannot handle playing Sheik against Meta Knight and are looking for a secondary, then this is problematic because Meta Knight will likely show up in at least 40% of your tournament matchups. Yeah, you'd be picking up a secondary that you use practically half the time.
Suggestions: Meta Knight, Snake, Wario, Diddy Kong, Marth, Pikachu, Ice Climbers
Ice Climbers
Sheik's most obviously bad matchup. Yes, she's got projectiles and can avoid getting grabbed... just like a whole lot of other characters. That doesn't exactly shift the matchup in her advantage when her actual options for disrupting the ICs are relatively minimal and she gets chaingrabbed by Popo alone. If you're actually planning on going all Sheik and braving this matchup, I salute your bravery, but wonder why you're reading this guide.
Suggestions: Zelda, Meta Knight, Snake, Wario, Zero Suit Samus, Peach, Mr. Game & Watch
Pikachu
Pikachu can chaingrab you if he lands a grab from like 0-15% or so. Deal with it.
Suggestions: Learning not to get grabbed at low %'s
Falco, Diddy Kong, Mr. Game & Watch
Uh... really? Do you seriously have that much of a problem with slightly disadvantageous matchups? Well, if you really feel the need to counterpick your way to a victory, and don't want to learn more than one other character...
Suggestions: Meta Knight, Snake, Falco, Diddy Kong, Mr. Game & Watch, Marth
I fear a stage.
Brinstar
This is one of those love-it-or-hate-it stages, based mostly on how comfortable you feel about moving around on a stage with acid, oddly placed side platforms, and uneven ground. If you've just had a bad experience on it, try first playing on it a bit more with Sheik before immediately looking for a secondary.
Suggestions: Meta Knight, Wario, Mr. Game & Watch, Pikachu, Donkey Kong
Frigate Orpheon
Okay, yeah, the right side is pretty scary for you. Another one of those stages I suggest actually practicing a bit on before you decide whether you actually hate it or not. Aside from the ledgeless right side during the initial form, this stage isn't actually terrible for Sheik.
Suggestions: Meta Knight, Mr. Game & Watch, Marth, Pikachu, R.O.B.
Jungle Japes
You really ought to ban this stage against Falco, you know. But if you didn't, and you get counterpicked to it, and your opponent is using Falco, then I guess you'll have to learn a secondary.
Suggestions: Snake, Falco, Diddy Kong, Wario, Mr. Game & Watch
Rainbow Cruise
Another one of those stages that you'll either be fine with or absolutely hate. In this case if you're having troubles with the stage you'll want to find a secondary that can better maneuver it.
Suggestions: Meta Knight, Mr. Game & Watch, King Dedede, R.O.B., Kirby
Final Destination, Battlefield, Smashville, Yoshi's Island, Lylat Cruise, Pokémon Stadium 1, Halberd
Dude. Dude. .... Really?
Suggestions: Finding a new main
If you have any other ideas or reasons to look for a secondary feel free to mention.