Tank Guards have low health, so best bet would be a Vet. 3 Volks squad with Mp40 along with a Grenadier w/ 2 Mg-42 or a KCH.
and with the Volks squad you can go overkill and use a Panzerfaust on them.
Flame. While I've been on the giving end of the spectrum, my Guards always had problems when hit with Flame (as long as I didn't micro vs V3 Pio).