House Sparrows like millet from the wildbird seed mixes we put out. They also like donuts, bread etc. Try simply using Black Oil Sunflower Seeds and Thistle/Nyjer and see what happens.
We are trying it here but we made the mistake of leaving out donuts for the chickadees (because we read that chickadees love them and we love the chickadees sooo….)
If you have any ideas other than this and crazy-bird-killing… I’d love to know. Let us know. We are sick of the House Sparrows.