As far as historical offerings go, I have no idea. There isn’t much evidence of a wide worship of Baldr (yet, so until we find something incredible, or we travel back in time, we really won’t know), so all I have is what is between the two of u/Us, and the little bits and pieces around the interwebs from His other people (though once again, there really aren’t that many, and it seems like most of them have either a peripheral, or a very private relationship with Him).
For me, I offer the obvious chamomile tea, usually with honey. I typically end up having tea with Him, enjoying my own cup as He enjoys His. I offer a few hours of candle burning (one of Beth’s Balder candles right now) on Sundays, as well as try to spend more time than usual with Him that day, although I think it may have to be a different day as the household’s schedule has been shifting, and weekends have become busier.
I also try to go out in nature or my garden and enjoy the beauty found there, I always feel Him around emphatically when I’m out in the wide wide. Honestly, I don’ think there is much that Baldr would say no to when offering to Him. I feel He really enjoys when we ourselves find joy in life, appreciating each moment for what it is and what it brings us; basically trying to live in the moment.