How would this work?

[Sir cryosin]

So the tricky domain cleric 2nd level ability to make a illusion duplicate of yourself. And you can cast spells from that duplicate. So say I was a vhuman with booming blade with 2lv's of trickery cleric and 18 rogue. Can I cast booming blade through the duplicate and still get the weapon and sneak attack dice?

[Unoriginal]

So the tricky domain cleric 2nd level ability to make a illusion duplicate of yourself. And you can cast spells from that duplicate. So say I was a vhuman with booming blade with 2lv's of trickery cleric and 18 rogue. Can I cast booming blade through the duplicate and still get the weapon and sneak attack dice?

Can you cast Booming Blade and sneak attack on the same turn?

You don't cast spells through the illusion, you just cast spells as if you were in the illusion's space. It doesn't give you additional actions.

[Sir cryosin]

Can you cast Booming Blade and sneak attack on the same turn?

You don't cast spells through the illusion, you just cast spells as if you were in the illusion's space. It doesn't give you additional actions.

Sneak Attack:
Beginning at 1st level you know how to strike subtly and exploit a foe's distraction. Once PER TURN, you can deal an extra 1d6 damage to one creature YOU HIT WITH AN ATTACK if you have advantage on the attack roll. The attack must use a finesse or ranged weapon.

So yes you can sneak attack with booming blade or any spell that has you make a attack with a weapon.

[Waterdeep Merch]

Sneak Attack:
Beginning at 1st level you know how to strike subtly and exploit a foe's distraction. Once PER TURN, you can deal an extra 1d6 damage to one creature YOU HIT WITH AN ATTACK if you have advantage on the attack roll. The attack must use a finesse or ranged weapon.

So yes you can sneak attack with booming blade or any spell that has you make a attack with a weapon.
The problem with it is you must make an attack with a melee weapon you are wielding first. Sneak attack is applied to weapon attacks only, no spells. So while you could have all the riders from booming blade go through the illusion, it wouldn't make much difference because those same riders need to hit the target of your weapon attack. It's just a strange way of doing the same thing as usual.

[Luppers]

The problem with it is you must make an attack with a melee weapon you are wielding first. Sneak attack is applied to weapon attacks only, no spells. So while you could have all the riders from booming blade go through the illusion, it wouldn't make much difference because those same riders need to hit the target of your weapon attack. It's just a strange way of doing the same thing as usual.
This, unfortunately the casting of booming blade requires a melee attack, which the duplicate can't make. No melee attack = automatic miss

[Zalabim]

You could maybe combine them all while using a Whip to hit a creature that's within your 10' reach but not adjacent.