Don't toss them! Some G4s are very common, but other G4s can sell for a decent price, depending on which character/version it is. I can't remember if there's a G4 price guide, but if you show us some photos, people here would be happy to help you ID and price them!
And even if they aren't worth much and you don't want to sell them, you can always put them up in the "freebies" section here, or donate them to a thrift store or something!
Yes, those are the McDonald's ponies... and they really don't go for much at all, as far as I know. You can always see if anyone would want them in the freebies area, but otherwise you might be best off just dropping them off at a thrift store.
Yes, I agree with Uftaki. Some G4’s can be worth a lot of money already (I myself have spent upto $50usd on one and that was cheap at the time I found her).
But unfortunately for these fast food ones they’re in abundance and don’t have a lot of monetary value. I’d put them up in the freebies, a lot of people do make some fun things out of the McDonald’s ones. Or just give them to a little kid you think may enjoy them?