Learn Russian: Потому что я всегда пью холодный кофе.

Пить is a high-frequency irregular verb. Instead of a normal ending, the root changes. You drop the -ить, keep the first letter п, add a soft sign (ь), and then the ending. For "I", it's я пью. The soft sign tells you to separate the sounds and pronounce the "yoo" clearly. The other forms follow this pattern: ты пьёшь, он/она пьёт, etc.

The word кофе ends in -е. Doesn't that usually make it a neuter word? Why does it use the masculine adjective холодный?

You have a good memory! Most Russian words ending in -е or -о are indeed neuter. However, кофе is a famous exception. It is a borrowed word and is historically masculine in Russian. Because it's masculine, any adjectives describing it must also be masculine, which is why we use холодный instead of the neuter холодное.

"Cold coffee" is the direct object here (the thing being drunk). Why doesn't холодный кофе change its ending for the accusative case?

Two things are happening here. First, кофе is a borrowed, foreign noun, meaning its ending never changes in Russian, no matter what grammatical case it is in. Second, for masculine inanimate objects (non-living things), the accusative case for adjectives looks exactly the same as the nominative (dictionary) form. So холодный stays exactly as it is!

Why is "because" written as two words (Потому что) here?