When to change from nipple to sippy cup.

My son is going to be 8 months in a few days he has two teeth and he just won't stop chewing up the nipples on his bottles 😫

I'm buying a pack of nipples every week. He can feed himself so I usually strap him into his rocker lean it back a bit and give him his bottle and he drinks and bites up the nipple. What cups can you recommend me to start him on?