I've searched both google and the site but looks like this hasn't been asked yet.
The closest Dementors have come to attacking a muggle is the attack on Harry and Dudley in the beginning of OotP.
Dementors seem to attack both Harry and Dudley, but I'm not sure the soul sucking of muggles has ever been mentioned.
Muggles can definitely sense them even though they can't see Dementors.
Could a Dementor suck the soul out of a muggle (and/or a squib)? What would the result look like to muggles? After an Avada Kedavra the muggles can at least tell the victim is dead. What would a soul-sucked muggle look like to other muggles?