I feel your pain. I totally went through the same thing with my first Yorkie. In fact, he's STILL finicky at 2. Aside from spending hundreds of dollars experimenting with various types of kibble/canned food, I would suggest trying raw. It's the ONLY thing Yoshi enjoys eating & will eat on a consistent basis. Mine actually prefer a Prey Model Raw diet. But you have to make that at home & it's tricky to get a proper protein/organ/bone ratio for a puppy. You can try giving them a bite of raw chicken or ground beef to see how they'll react. From there, you can try a premade raw like Primal or Stella & Chewy's.
Not everyone is a "raw person". Some say that raw shouldn't be fed to puppies. All of my puppies have thrived on a raw diet. But that's just me. So if you're opposed to raw, you can try a freeze-dried raw. You just crumble the nugget & add a little water. Our favorite is Primal. We also eat Stella & Chewy's occasionally. Most finicky pups will eat freeze-dried raw. Other palatable brands that have worked for us are Vital Essentials Freeze-Dried Nuggets & Orijen Regional Red. ORR is a kibble. It's a large kibble, so I cut it in half with kitchen shears. I do the same with the Vital Essentials.
I'm not sure what types of food stores you have near you. Primal, Stella's, Vital Essentials & Orijen are all available from Chewy.com & they ship super fast. Those brands are typically available at the smaller, independent stores. Nature's Variety makes a frozen raw that is available at Petco.
You can also try home cooking if you have time. But it's really important to get a good supplement like BalanceIt.
I hope that helps a little. I've been there & I know how you feel like your life revolves around getting them to eat. It's so frustrating. Especially when you think you've found something they like, then they turn their nose up at it the next day. You can PM me if you want some other suggestions. I have a lot

GOOD LUCK!!
One more thing...if they REALLY won't eat ANYTHING, you might want to check in with your vet just to make sure they're okay physically. Good luck!