I have an observation hive in my classroom in NY, not much food left, wondering if I can feed bee tea (1:1 sugar/water) now.
Yes. If the weather is cold, they may be fooled into thinking there is a flow going on & rush out & freeze. If you can restrict the feeder or plug the exit you (they) should be fine.
Feed them 5:3 or 2:1. No reason to mess around with 1:1 which will spoil quickly and cause moisture problems.