Do Your Plants Prefer Tea Or Coffee?

I’ve recently been told two different bits of advice, and I’d like to know what you think ...

My sister tells me that her roses flourish due to being fed a constant supply of coffee grounds (and take it from me, my sister can drink a lot of coffee ...).

Our call centre manager at Two Wests tells me that the way to grow good, strong sunflowers is to feed them with tea!

So, I’ve somewhat of a dilemma ... I don’t drink tea or coffee, so should I be adding PG Tips and filter coffee to my weekly shop to give a caffeine fix to my plants or should I just ‘let them drink water’ (echoes of Marie Antoinette) ...