I only drink decaf tea, and I let my lil boy have some of mine when he asks but I literally just pour a bit into a cup for him. I don't think it's recommended in large quantities though as the tannins in tea prevent mineral and vitamin absorption, which are present in both normal and decaf tea. Have you thought about maybe just flavouring water? Or adding water to cows milk?
My little one has a little cup of decaf tea and oat milk, specially if he’s with my mom as he always wants to try hers x
My little girl refused cows milk for a few months ( only had 1 night time bottle) I slowly started adding cows milk into her formula until it got to a full bottle of cows milk and she never refused it that way. My little girl was also fine with water until she had hand foot & mouth and started refusing plain water so we started adding a tiny bit of juice into it to get her to have a drink, that could maybe work for you to?
There's still a trace of caffeine in decaf so I don't let my mum give my LO though she wants to. My boy drinks a ton of water and milk so no need. Your situation is a but different but I would start with camomile tea or even squash as more age appropriate. Can also add a bit of a prune pouch to water and mix
Also wanted to add that I haven’t given him a bottle of tea before but just trying to find a solution to see if he can have it instead of a couple bottles of formula milk