I like the iron-on stabilizer best for knits. It doesn't let you stretch the knit in the hoop, which could make it distort. Plus, the non-iron-ons can pull in the knit even if it is hooped with stabilizer if they're not actually stuck together. So the sticky stabilizers should work too, but I haven't tried them.
Depending on the fabric of the tank top and how thin and stretchy it is, I would first consider using a cut away poly mesh for the best stablization as tank fabrics tend to be very stretchy and not very heavy. JMHO