3 Weeks Post-op Tummy Tuck - Popping Noise After Sneezing?

Generally speaking the plication of the abdominal wall is very secure and it would take significant force / trauma to disrupt this repair. Generally speaking, a sneeze, cough and/or straining will not generate enough force to harm the repair. Again, if you are concerned, I would suggest that you visit with your surgeon for an examination so that he/she can (most likely) put your mind at ease.Best wishes.

This is probably the first time I have heard this and I would need to know more aobut your surgery and the method of muscle or diastasis repair. Occasionally incidental hernias are fixed with mesh and you may be experiencing clicking or popping of mesh or permanent sutures.

3 Weeks Post-op Tummy Tuck - Popping Nose After Sneezing?
Can a Popping Noise After Sneezing Be Scar Tissue? Can Scar Tissue Already for 3 Weeks Post-op?

I cant say I have ever heard a complaint like this but I would be evaluated by your plastic surgeon.  Scar tissue would not be a cause of the noise you are hearing.  If there is not bulging, swelling or pain associated with it, it is unlikely anything to worry about, but again I would recommend seeing your plastic surgeon.

Good luck.