You could use your own energy to bless it, just visualize a sphere of energy(of any color, whatever you want, depending what the blessing is for) and let it surround the tea or place it inside the tea and let it slowly disslove into the tea and visualize what you want the blessing to do for you. It's fairly simple but may take some tries. If you think about it, your magick(energies) are much like mucules. The more you work them out, the stronger they get.
You can also ask a god or goddess or a spirit if you have/believe any to bless it for you. Or use candles(extracting its energy into tea using your magick) or surround it with crystals to bless it.(Any color, depending on what blessing it is, also, research the crystals spiritual and energy properties. Knowing that can help. Example: Rose Quartz gives off loving and calming energies. And for candles: white, the color is widely known for purity and peace.)
I hope this helps.