Sara just a thought, my son drank cows milk from a bottle but WOULD NOT drink out of a cup or a sippy....I thought and thought about it, got quite stressed because I was worried about him having a bottle when DD arrived (silly in hindsite), one day I gave him a cup of milk with a spoon in it....
....he LOVED it.
Kept giving him a spoon for the next few weeks and suddenly he was happy to drink it from the cup.
Just a thought, sometimes they just don't like that it's in a "new form" and it's not so much about the milk. Might be worth a try

Hugs to you Deb for the food issues your kids have, I think you do a sensational job tbh xx Having been on a fairly loose ED with DD I can only imagine how hard it must be when you can't have little slip ups! Not saying I feel sorry for you, but rather I admire your strength!