How do I train my puppy to not eat random things on the ground while on a walk?

I’m having such a hard time with this. I can’t differentiate if she’s sniffing around to go pee, or if she’s sniffing around to find something to eat. And once she finds it there’s no time for me to react and it’s too late – she’s already trying to eat it.

There’s no chance of me physically taking it out of her mouth because she has bitten me before and drawn blood.

Please share ideas.