I wouldn't drink 3% store brand variety H2O2 (Hydrogen-Peroxid) if you paid me. There are way too many fixers and stabilizers in it that can't be good for human health. The brown bottle variety from drug stores should only be used topically or questionably as a mouth rinse.
Food grade H2O2 (Hydrogen-Peroxid) is quite a different matter. It usually comes in 35% strength and must be diluted with pure water for everyday use. It can be used as drops full strength in whole glasses of water for ingestion. It does not contain the fixers and stabilizers that store brand 3% H2O2 (Hydrogen-Peroxid) contains.
You can read a bit about H2O2 and it's uses at: