Tea

I don't think you'll get that type of strength from more tea or loose leaf tea, but you can always make an experiment:

Do 10x what you usually would, like 10 teabags to a cup of water, and let steep overnight. Then dilute that until you get the flavor you want. 1 parts concentrate to 4-5 parts water is what's usually used in Russian tradition (with samovar and chainik), and the concentrate by itself might actually be bad for you if you drink a lot of it (like a whole pot, a cup is mostly safe).

If you want to be all scientific and advanced about it, you can also try to notice how the flavor profile changes with different concentrations.

But from your description I would guess that you're after more punchy flavors, which are usually from blends with flavor oils (like the bergamot in Earl Grey) and/or the flavor enhancers. If you can't do sugar, you could try Stevia or artificial sweetener to get some of that kick without it.

Lapsang Souchang is one of the most famous and smokiest teas, with a very clear smoky flavor that could work.

But beyond that, feel free to try loose leaf, but I'm afraid you've had to have very very bad/old teas for them to be watery at a bag steeped for two minutes, not to mention your recipes.