Does drinking warm water in the morning do anything?

It is pleasant and harmless, and the specific claims made for it are largely unsupported. There is no good evidence that warm water detoxifies anything, burns fat, or boosts metabolism meaningfully. What is true is milder: any fluid after a night without drinking addresses mild overnight dehydration, warm liquid can help some people with morning bowel regularity, and having a fixed first action is a useful habit anchor. Adding lemon does not change the body's pH, which is tightly regulated regardless. If you enjoy it, keep it — just do not expect it to substitute for anything.