Can I donate Fast Offerings to a different ward online?

I want to donate to funeral expenses for a family not in my ward. I was told to donate fast offerings to that family's ward. Can I do that using the online donations tool?

No. Even if you did, it wouldn't make a difference. All Fast Offering funds are immediately swept to church headquarters. So regardless of what ward you donate to, it ends up in the same place.

Nor does it change the funds that are available to the ward.

The only thing it might change is that wards that disburse more than they take in may receive increased scrutiny from the church.

To me it's a bit like if a friend was having surgery and required a blood transfusion, I could go to my local blood donation center and donate. Even if my blood wasn't actually used for my friend, when my friend and his family know that I donated blood, they'll consider it as if I had donated directly to my friend.

For cases when someone desires a more direct way to donate to specific funeral expenses, often the family can put you in contact directly with the funeral home, or you could pay for something like flowers, or make a contribution to a foundation the family is directing funds towards.