"How much tea do you drink?"
Translation:तू कितनी चाय पीता है?
The confusion is because in the "lightbulb" to the Numbers lesson, it states that adverbs do not change form by sex or number, yet कितना is an adverb. More specifically, in the English Wiktionary कितना is classified as an adverb, yet the English "how much" is broken down into either determiner or adverb, depending on use. So, when used to modify a verb, then "how much" is an adverb, and this agrees with the lesson here that कितना must not change with verbs and that adverbs don't decline (change form).
This gets a little trickier when "how much" is a determiner. "How much cheese is there?" uses it in conjunction with a noun, so here everything is clear — it would decline in Hindi, exactly as in this example with "tea". Wiktionary also gives the examples "How much is left in the fridge?" and "How much is it?" under "Determiner", though one could assume "how much" modifies "is" here and is therefore an adverb. This is where it gets tricky in drawing parallels to Hindi. I wonder how a sentence like "How much is left in the fridge?", where there is no explicitly stated object, would translate in Hindi.
Really, I hate determiners. They are a headache in German too, where sometimes "ihr" is classified as a determiner, sometimes as a pronoun.