Caffeine affects some people more than others. Generally speaking, it also depends on the source and amount of caffeine consumption.
Tea is generally less stimulating to the mind, than coffee. Green tea is better. Having said that, some people don’t seem to have a problem with drinking coffee, and the effect on the meditation. You have to find what works for you.
Generally, caffeine being a stimulant is what causes too much thought-energy in the mind, so there should be a balance. This is why I recommend tea, especially green tea, as this balances out the caffeine with something known as L-Theanine. This activates alpha brainwaves, which are associated with mild meditative states.
My statement about caffeine is to not allow it to become an addiction. Meaning, don’t get cranky if you don’t have coffee around 🙂
Don’t allow any form of consumption to become a crutch for the mind or body. What’s more important is to find internal sources of pleasure and joy and energy, i.e., the mind itself. The way to do that is through meditation.
A great caffeine replacement is to do Compassion meditation in the morning. This activates and arouses the gamma field of brainwaves. These are associated with more energy, that is stable, non-stimulating, and keeps the mind in a process of a flow state. Plus, it feels good! 🙂