Loki: burnt offerings. Acts of hardships done in his honor. Always with a fire Etin burn foods and drinks. So burnt drink. To black type of burnt drinks. Mead is good for him.
Fenrir: not real big on offerings. If any offerings offer him animal shins and meat from animals you have hunted. Or acts of vengeance don't in his honor.
Hela: decaying pieces of meat. Rotting roses, and acts don't in her honor. Not real big on actual physical offerings, but more on acting or doing offerings.
Jormungand: not real big on offerings, but if any do acts of valor in his/her honor.
As for any is Etin you should make offerings like berries and stuff. Even acts of valor done in their name.
This concludes my article on Etin and rokkr offerings,