I have a strange itchy rash on the top of toes. Could this be reaction to antibiotics I am taking for a sinus infection? It's augmentum.

Reaction to antibiot. The chance that this is a reaction to the antibiotic are slim, as an allergic reaction will usually start centrally, and not in the periphery. It is still possible, but not likely. Allergy will come about as a fine rash, up to hives, and are very itchy. You may have a different issue, but I would suggest you see your doctor to lood at the rash, diagnose this and give you appropriate treatment.
Yes. It is possible to be drug reaction. If it starts to get worse call doctor and stop medication. Antibiotics are often not useful for uncomplicated sinus infection.
Doubt it. The general rule is that any drug can cause any sort of rash, but I've never seen Augmentin (amoxicillin and clavulanate) cause a rash on the feet. More likely, you're having an allergic or irritant reaction to something, possibly your shoes or some component of them. A dermatologist can give you a more precise diagnosis after examining you.