At this time fo year trees start pumping sap around their system in their phloem (inner bark). You can collect and drink this by tapping an suitable tree, including Birch, Sycamore, or Maple.
Drill a hole about 1-2 inches deep into the trunk, at knee height. Insert a clean stick and collect the sap that drips off in a container. on the ground. Cover the container with cotton or mesh to strop debris getting in. Wait 3-24 hours. You can also insert tubing into the hole to run the sap out.
Unfortunately this method opens up the tree to infection by fungal spores which can damage it.
More sustainably, take a branch and tie it branch down to the ground, Slice the tip off the branch and secure it inside a bottle e.g. with duck tape. The sap will drip out of the end of the branch. It's much less liely that a fungal infection will be able to travel down the branch into the trunk using this method.
Use the Sap
The sap contains electrolytes and vitamins that would have been sustaining for ancient people who had gone through winter with minimal fresh fruits or vegetables. You can drink it neat for a refreshing pick me up.
Or try boiling it down into syrup to use on desserts - but you'll only get an egg cup of syrup out of a pint of sap.
Alternatively, try brewing it into wine.