tanken
to refuel / fill up
To put fuel such as gasoline or diesel into a vehicle's tank.
Ich muss noch tanken, bevor wir auf die Autobahn fahren.
I still need to fill up before we get on the highway.

to refuel / fill up
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to refuel / fill up
To put fuel such as gasoline or diesel into a vehicle's tank.
Ich muss noch tanken, bevor wir auf die Autobahn fahren.
I still need to fill up before we get on the highway.

The verb 'tanken' (to refuel/fill up) derives directly from the noun 'der Tank' (the tank). This connection to the basic meaning 'to fill a container' helps you remember the word.
Der Tank ist fast leer, wir müssen gleich tanken.
The tank is almost empty; we need to fill up soon.
In its main meaning, 'tanken' (to refuel/fill up) can be used without an object when it is clear that it refers to the vehicle. But you can also add an object to specify what you are filling up with.
Warte kurz, ich muss noch schnell tanken.
Wait a moment, I still need to fill up quickly.
In the figurative meaning, 'tanken' (to soak up/recharge) is often combined with positive, abstract things. Common phrases are 'Sonne tanken' (to soak up the sun), 'Kraft tanken' (to regain strength), 'Energie tanken' (to recharge one's energy), or 'Selbstvertrauen tanken' (to gain self-confidence).
Nach der anstrengenden Woche muss ich am Wochenende neue Kraft tanken.
After the exhausting week, I need to regain some strength over the weekend.
The meaning 'to drink alcohol' is very colloquial and should only be used in very informal situations among friends. It often implies that larger amounts are being drunk.
Was habt ihr am Samstag gemacht? – Wir waren erst was essen und haben dann noch ordentlich getankt.
What did you do on Saturday? – We went out to eat first and then had a proper drinking session.
to drink
'trinken' and 'tanken' can both have to do with alcohol, but they are not equally neutral. 'trinken' is the normal word when someone takes in a liquid. It can also mean that someone drinks alcohol regularly or too much. In this context, 'tanken' is used only colloquially and often somewhat negatively or jokingly when someone drinks a lot of alcohol. Learners may confuse the words because in German people sometimes say that someone has 'getankt'. But for water, coffee, or normal drinks, you almost always say 'trinken'.

Auf der Feier hat Paul zu viel getankt und ist früh nach Hause gegangen.
At the party, Paul drank too much and went home early.
Nach dem Training trinke ich erst einmal ein großes Glas Wasser.
After training, the first thing I do is drink a large glass of water.